BRCA1 C-terminal Research Articles

Abstract 3892: Discovery and analysis of COMMD1 in the DNA damage response network

Abstract Spatially distinct domains impart functionality to the proteins and are often under evolutionary pressure to maintain sequence and/or structure. The BRCA1 C-terminal (BRCT) domain has an established role in cancer susceptibility and in the DNA damage response (DDR), as mutations in cases of familial breast cancer often result in a truncated protein lacking the two BRCT domains which are required for interactions with proteins such as p53, ABRAXAS, BACH1, and CtIP. BRCT domains can occur as singletons or as tandem domains (tBRCT) that function as a single cohesive structural unit involved in binding phosphorylated peptides targeted by PI3K-like proteins such as ATM in response to DNA damage. Using the Yeast Two-Hybrid system (Y2H) as well as Tandem Affinity Purification coupled to mass spectrometry (TAP-MS), we have built a domain centric protein-protein interaction network for a subset of tBRCT domains from BRCA1, TP53BP1, LIG4, PAXIP1, ECT2, BARD1, and MDC1. Evaluation of this network has revealed a number of interesting interactions and highlighted the interconnectivity potential found in these domains. Analysis of this network has revealed several interesting proteins that are highly interconnected with tBRCT domains, such as COMMD1 (an important regulator of copper homeostasis, sodium transport, NF-κB, and HIF-1), which has not yet been characterized to participate in the DDR, but was found to interact with the tBRCT domains of BARD1, BRCA1, and LIG4. Furthermore, an earlier Y2H screen conducted by our laboratory found COMMD1 as an interaction partner of CHK2. Therefore, we sought to determine the role of COMMD1 in response DNA damaging agents. Convincingly, the levels of COMMD1 are inversely related to apoptotic induction caused by cisplatin and doxorubicin. Furthermore, CHK2 signaling appears to control the ability of COMMD1 to enhance cisplatin induced apoptosis as wild type but not CHK2-/- HCT116 cells exhibited a repression in cisplatin induced apoptosis when COMMD1 was over expressed. These results indicate the importance of COMMD1 for cellular susceptibility to traditional chemotherapeutics. Currently, we are exploring the mechanisms by which COMMD1 in coordination with tBRCT domain containing proteins and CHK2 sensitizes cells to DNA damaging agents. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3892. doi:10.1158/1538-7445.AM2011-3892

Abstract 2377: Variation in the BRCT1 domain of the DNA repair gene XRCC1 delays invasive breast cancer in mice

Abstract The breast cancer susceptibility protein BRCA1 C-terminal (BRCT) domain coordinates protein interactions in DNA repair and cell cycle control, and comprises over 100 member proteins. One of these, XRCC1, is involved in base excision repair and single strand break repair. In order to investigate the role of the XRCC1-BRCT1 domain in breast cancer, we generated a mouse line with a variation of leucine (L) from arginine (R) at position 360, and crossed it with PyMT transgenic mice with a highly penetrant metastatic breast cancer phenotype. PyMT mice with advanced tumors expressing the L360R variant (N=20) had an average tumor volume of 360±57 mm3 compared to an average tumor volume of 730±69 mm3 for PyMT/wild type littermates (N=20), significant at p less than 0.01. In addition, the L360R variant was associated with a significant decrease in metastatic foci in the lungs of PyMT mice, an increase in tumor cell apoptosis as measured by caspase 3 immunohistochemistry, a decrease in tumor cell proliferation as measured by ki-67 immunohistochemistry, and a decrease in PARP binding as determined by NADH depletion. These preliminary observations suggest that the XRCC1/BRCT1 domain is involved in invasive breast cancer, and that genetic variation of this domain can suppress the invasive phenotype by decreasing tumor cell proliferation and increasing apoptosis of tumor cells possibly in association with altered PARP binding and activity. The XRCC1 L360R mouse is a promising animal model to further investigate the potential of targeting the XRCC1/BRCT1 domain for adjunctive treatment of invasive breast cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2377. doi:10.1158/1538-7445.AM2011-2377

Human TopBP1 localization to the mitotic centrosome mediates mitotic progression

TopBP1 contains repeats of the BRCA1 C-terminal (BRCT) domain and plays important roles in DNA damage response, DNA replication, and other cellular regulatory functions during the interphase. In prometaphase, metaphase, and anaphase, TopBP1 localizes to the mitotic centrosomes, which function as spindle-poles for the bipolar separation of sister chromatids. The localization of TopBP1 to the mitotic centrosomes is mediated by amino acid residues 1259 to 1420 in the TopBP1 C-terminal region (TbpCtr). GST and DsRed2 tags fused to TbpCtr were localized in the mitotic centrosomes, thereby suggesting that TbpCtr functions as a mitosis-specific centrosome localization signal (CLS). Mutations of Ser 1273 and/or Lys 1317, which were predicted to interact with a putative phosphoprotein, inhibited CLS function. Ectopic expression of TbpCtr specifically eliminated endogenous TopBP1 from the mitotic centrosomes, whereas mutant TbpCtr derivatives, containing substitutions at Ser 1273 and/or Lys 1317, did not. The specific elimination of TopBP1 from the mitotic centrosomes prolonged the durations of prometaphase and metaphase and shortened the inter-kinetochore distances of metaphase sister chromatids while maintaining the spindle assembly checkpoint. These results suggest that the localization of TopBP1 to the mitotic centrosomes is necessary for proper mitotic progression.

A novel role for BRCA1 in regulating breast cancer cell spreading and motility.

BRCA1 C-terminal (BRCT) domains in BRCA1 are essential for tumor suppressor function, though the underlying mechanisms remain unclear. We identified ezrin, radixin, and moesin as BRCA1 BRCT domain-interacting proteins. Ezrin-radixin-moesin (ERM) and F-actin colocalized with BRCA1 at the plasma membrane (PM) of cancer cells, especially at leading edges and focal adhesion sites. In stably expressing cancer cells, high levels of enhanced green fluorescent protein (EGFP)-BRCA1(1634-1863) acted as a dominant-negative factor, displacing endogenous BRCA1 from the PM. This led to delayed cell spreading, increased spontaneous motility, and irregular monolayer wound healing. MCF-7 cells (intact BRCA1) showed lower motility than HCC1937 cells (truncated BRCA1), but expression of EGFP-BRCA1(1634-1863) in MCF-7 increased motility. Conversely, full-length BRCA1 expression in HCC1937 decreased motility but only if the protein retained ubiquitin ligase activity. We conclude that full-length BRCA1 is important for complete tumor suppressor activity via interaction of its BRCT domains with ERM at the PM, controlling spreading and motility of cancer cells via ubiquitin ligase activity.

Cell cycle-dependent conjugation of endogenous BRCA1 protein with SUMO-2/3

BackgroundBRCA1, the main breast and ovarian cancer susceptibility gene, has a key role in maintenance of genome stability, cell cycle and transcription regulation. Interestingly, some of the numerous proteins which interact with BRCA1 protein undergo conjugation with small ubiquitin-like modifiers (SUMO). This post-translational modification is related to transcription, DNA repair, nuclear transport, signal transduction, and to cell cycle stress response. Methods and resultsProtein sequence analysis suggests that sumoylation target sites belong to the RING finger and BRCT domains (BRCA1 C-terminus), two crucial regions for BRCA1 function. Moreover putative SUMO interacting motifs are present in the sequence of many proteins of BRCA1 network. Using immunoprecipitations and western blotting, we show the conjugation of endogenous nuclear BRCA1 protein with SUMO-2/3. BRCA1 conjugation with SUMO-2/3 is linked to the cell cycle in a cell line dependent manner since no cell cycle dependence of sumoylation is observed in MCF7 breast cancer cells. In contrast, BRCA1 conjugation with SUMO-2/3 is linked to the oxidative stress independently to the cell line, in DU145, MCF7 and 293 T cells. Conclusion and general significanceOur data reveal a new BRCA1 regulation pathway implying sumoylation in response to cell cycle progression and oxidative stress, providing a possible mechanism for the involvement of BRCA1 gene in tumorigenesis.

Tandem BRCT Domains: DNA's Praetorian Guard

The cell's ability to sense and respond to specific stimuli is a complex system derived from precisely regulated protein-protein interactions. Some of these protein-protein interactions are mediated by the recognition of linear peptide motifs by protein modular domains. BRCT (BRCA1 C-terminal) domains and their linear motif counterparts, which contain phosphoserines, are one such pair-wise interaction system that seems to have evolved to serve as a surveillance system to monitor threats to the cell's genetic integrity. Evidence indicates that BRCT domains found in tandem can cooperate to provide sequence-specific binding of phosphorylated peptides as is the case for the breast and ovarian cancer susceptibility gene BRCA1 and the PAX transcription factor-interacting protein PAXIP1. Particular interest has been paid to tandem BRCT domains as "readers" of signaling events in the form of phosphorylated serine moieties induced by the activation of DNA damage response kinases ATM, ATR, and DNA-PK. However, given the diversity of tandem BRCT-containing proteins, questions remain as to the origin and evolution of this domain. Here, we discuss emerging views of the origin and evolving roles of tandem BRCT domain repeats in the DNA damage response.

Abstract 1117: Characterization of BAT1 (UAP56) interaction with BARD1

Abstract BARD1 (BRCA1-associated ring domain 1) was originally identified in a yeast-two-hybrid screen as a binding partner of BRCA1. The functional heterodimer BRCA1-BARD1 is required for several of the cellular and tumour-suppressor functions of BRCA1. Both proteins interact through the N-terminal RING domain to form a heterodimeric E3 ubiquitin ligase that constitutes the major catalytic activity of the BRCA1-BARD1 complex. BARD1 is also associated to p53-mediated apoptosis, in a BRCA1-independent manner. The carboxy terminus of BRCA1 is highly acidic and contains two tandem BRCA1 C-terminal (BRCT) domains, which are characteristic of members of a large superfamily of proteins involved in DNA repair and cell cycle checkpoint control. These domains are protein-protein interacting regions that mediate the association with a number of other proteins with a role in DNA replication, DNA damage repair (DDR) pathway, transcription, cell cycle control, and ubiquitination. BARD1 also contains two tandem BRCT repeats at its C-terminus, a region shown to bind serine-phosphorylated peptides in vitro. In order to identify putative interaction-proteins with BARD1 C-terminal region we performed a yeast two hybrid (Y2H) screening using BARD1 BRCT tandem domain (aa 554-777) to screen a human testis cDNA library. We identified, among other hits, a cDNA coding for residues 308-418 of BAT1 (UAP56, C-terminal region [OMIM 142560]). UAP56 is a member of DEAD box family of ATP-dependent RNA helicases. Several studies indicate that UAP56 protein is not only essential in pre-mRNA splicing but is also important in mRNA nuclear export and cytoplasmic mRNA localization. We confirmed BAT1-BARD1 interaction by conducting co-IP analysis of ectopic expressed BARD1 and BAT1 in HEK293T cells. We are using a Y2H system approach to determine the minimal region of interaction between BARD1 and BAT1; in parallel, we are also checking for the presence of a multicomponent complex, investigating the presence of BRCA1. In order to assess the biological significance of the interaction between BARD1 and BAT1 we will determine whether this interaction is important for the activation of, or recovery from, the G2/M cell cycle checkpoint after IR and also investigate its putative involvement in p53-dependent apoptosis pathway. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1117.

A cooperative activation loop among SWI/SNF, γ-H2AX and H3 acetylation for DNA double-strand break repair

Although recent studies highlight the importance of histone modifications and ATP-dependent chromatin remodelling in DNA double-strand break (DSB) repair, how these mechanisms cooperate has remained largely unexplored. Here, we show that the SWI/SNF chromatin remodelling complex, earlier known to facilitate the phosphorylation of histone H2AX at Ser-139 (S139ph) after DNA damage, binds to gamma-H2AX (the phosphorylated form of H2AX)-containing nucleosomes in S139ph-dependent manner. Unexpectedly, BRG1, the catalytic subunit of SWI/SNF, binds to gamma-H2AX nucleosomes by interacting with acetylated H3, not with S139ph itself, through its bromodomain. Blocking the BRG1 interaction with gamma-H2AX nucleosomes either by deletion or overexpression of the BRG1 bromodomain leads to defect of S139ph and DSB repair. H3 acetylation is required for the binding of BRG1 to gamma-H2AX nucleosomes. S139ph stimulates the H3 acetylation on gamma-H2AX nucleosomes, and the histone acetyltransferase Gcn5 is responsible for this novel crosstalk. The H3 acetylation on gamma-H2AX nucleosomes is induced by DNA damage. These results collectively suggest that SWI/SNF, gamma-H2AX and H3 acetylation cooperatively act in a feedback activation loop to facilitate DSB repair.

PTIP promotes DNA double‐strand break repair through homologous recombination

PTIP (Pax2 transactivation domain-interacting protein) is a large nuclear protein containing six BRCT (BRCA1 C-Terminal) domains. PTIP is recruited to DNA-damage sites through its BRCT domains and thus has been implicated in the DNA damage response. To define the function of PTIP in DNA repair, we disrupted the PTIP gene of the chicken DT40 B cell line. PTIP mutant (PTIP(-/-/-) ) cells displayed phenotypes frequently observed in cells with defective homologous recombination (HR), i.e. a marked increase in the number of spontaneously arising DNA lesions as well as sensitivity to ionizing radiation (IR) and the topoisomerase I inhibitor, camptothecin. Accordingly, analysis of HR efficiency by using artificial recombination substrates showed that the HR efficiency was reduced in the PTIP-deficient chicken and the PTIP-depleted HeLa cells. As microarray analysis showed no apparent difference between wild-type and PTIP(-/-/-) cells in the expression of known HR factors, it is unlikely that this reduction in HR efficiency in PTIP-deficient cells is associated with PTIP's role in transcriptional regulation. We thus propose that PTIP promotes double-strand break repair through a direct role in HR.

A Supramodular FHA/BRCT-Repeat Architecture Mediates Nbs1 Adaptor Function in Response to DNA Damage

The Mre11/Rad50/Nbs1 protein complex plays central enzymatic and signaling roles in the DNA-damage response. Nuclease (Mre11) and scaffolding (Rad50) components of MRN have been extensively characterized, but the molecular basis of Nbs1 function has remained elusive. Here, we present a 2.3A crystal structure of the N-terminal region of fission yeast Nbs1, revealing an unusual but conserved architecture in which the FHA- and BRCT-repeat domains structurally coalesce. We demonstrate that diphosphorylated pSer-Asp-pThr-Asp motifs, recently identified as multicopy docking sites within Mdc1, are evolutionarily conserved Nbs1 binding targets. Furthermore, we show that similar phosphomotifs within Ctp1, the fission yeast ortholog of human CtIP, promote interactions with the Nbs1 FHA domain that are necessary for Ctp1-dependent resistance to DNA damage. Finally, we establish that human Nbs1 interactions with Mdc1 occur through both its FHA- and BRCT-repeat domains, suggesting how their structural and functional interdependence underpins Nbs1 adaptor functions in the DNA-damage response.

DNA Double-Strand Breaks Come into Focus

The Mre11-Rad50-Nbs1 (MRN) complex senses DNA double-strand breaks and recruits different repair pathway and checkpoint proteins to break foci. Two new studies (Williams et al., 2009; Lloyd et al., 2009) identify Nbs1 as a key factor in this process and reveal how an N-terminal protein recruitment module in Nbs1 binds to different response factors through shared phosphopeptide motifs.

Maintenance of the DNA-Damage Checkpoint Requires DNA-Damage-Induced Mediator Protein Oligomerization

Oligomeric assembly of Brca1 C-terminal (BRCT) domain-containing mediator proteins occurs at sites of DNA damage. However, the functional significance and regulation of such assemblies are not well understood. In this study, we defined the molecular mechanism of DNA-damage-induced oligomerization of the S. cerevisiae BRCT protein Rad9. Our data suggest that Rad9's tandem BRCT domain mediates Rad9 oligomerization via its interaction with its own Mec1/Tel1-phosphorylated SQ/TQ cluster domain (SCD). Rad53 activation is unaffected by mutations that impair Rad9 oligomerization, but checkpoint maintenance is lost, indicating that oligomerization is required to sustain checkpoint signaling. Once activated, Rad53 phosphorylates the Rad9 BRCT domain, which attenuates the BRCT-SCD interaction. Failure to phosphorylate the Rad9 BRCT results in cytologically visible Rad9 foci. This suggests a feedback loop wherein Rad53 activity and Rad9 oligomerization are regulated to tune the DNA-damage response.

The Structure of Fcp1, an Essential RNA Polymerase II CTD Phosphatase

Kinases and phosphatases regulate mRNA synthesis and processing by phosphorylating and dephosphorylating the C-terminal domain (CTD) of the largest subunit of RNA polymerase II. Fcp1 is an essential CTD phosphatase that preferentially hydrolyzes Ser2-PO(4) of the tandem YSPTSPS CTD heptad array. Fcp1 crystal structures were captured at two stages of the reaction pathway: a Mg-BeF(3) complex that mimics the aspartylphosphate intermediate and a Mg-AlF(4)(-) complex that mimics the transition state of the hydrolysis step. Fcp1 is a Y-shaped protein composed of an acylphosphatase domain located at the base of a deep canyon formed by flanking modules that are missing from the small CTD phosphatase (SCP) clade: an Fcp1-specific helical domain and a C-terminal BRCA1 C-terminal (BRCT) domain. The structure and mutational analysis reveals that Fcp1 and Scp1 (a Ser5-selective phosphatase) adopt different CTD-binding modes; we surmise the CTD threads through the Fcp1 canyon to access the active site.

MDC1 regulates intra-S-phase checkpoint by targeting NBS1 to DNA double-strand breaks

The product of the Nijmegen breakage syndrome gene (NBS1) plays crucial roles in DNA damage response through its association with many proteins, including MRE11 and RAD50. However, it remains to be determined exactly how NBS1 accumulates at or near DNA double-strand breaks. Here we report that MDC1 directly binds to NBS1 and targets NBS1 to the sites of DNA damage. The MDC1-NBS1 interaction occurs through a specific region (residues 200-420) of MDC1, which contains multiple consensus casein kinase 2 (CK2) phosphorylation sites. In addition, this interaction requires both the forkhead-associated (FHA) and tandem BRCA1 C-terminal (BRCT) domains of NBS1. Disruption of the MDC1-NBS1 interaction results in failure of NBS1 accumulation at DNA double-strand breaks and impairment of intra-S checkpoint activation. These studies provide important mechanistic insights as to how MDC1 regulates NBS1 and the intra-S-phase checkpoint in response to DNA damage.

A yeast recombination assay to characterize humanBRCA1missense variants of unknown pathological significance

The BRCA1 tumor suppressor gene is found mutated in familial breast cancer. Although many of the mutations are clearly pathological because they give rise to truncated proteins, several missense variants of uncertain pathological consequences have been identified. A novel functional assay to screen for BRCA1 missense variants in a simple genetic system could be very useful for the identification of potentially deleterious mutations. By using two prediction computer programs, Sorting Intolerant from Tolerant (SIFT) and Polymorphism Phenotyping (PolyPhen), seven nonsynonymous missense BRCA1 variants likely disrupting the gene function were selected as potentially deleterious. The budding yeast Saccharomyces cerevisiae (S. cerevisiae) was used to test these cancer-related missense mutations for their ability to affect cell growth and homologous recombination (HR) at the HIS3 and ADE2 loci. The variants localized in the BRCA1 C-Terminus (BRCT) domain did not show any growth inhibition when overexpressed in agreement with previous results. Overexpression of either wild-type BRCA1 or two neutral missense variants did not increase yeast HR but when cancer-related variants were overexpressed a significant increase in recombination was observed. Results clearly showed that this genetic system can be useful to discriminate between neutral and deleterious BRCA1 missense variants.

A novel domain of BRCA1 interacts with p53 in breast cancer cells

The interactions between BRCA1 and p53 are relevant for understanding hereditary breast and ovarian cancer. Although in vitro studies reported that BRCA1 (amino acids 224–500) and the second BRCT domain of the BRCA1 C-terminus may interact with p53, quantitative biophysical measurements indicate that these regions of BRCA1 do not bind efficiently to p53. Here we show that BRCA1 interacts with p53 in vivo in breast cancer cells, through another BRCA1 domain (amino acids 772–1292). Expression of a truncated BRCA1 (amino acids 772–1292) stimulated p53 DNA-binding and transcription activities and apoptosis, recapitulating some effects of DNA damage. These results suggest that a novel domain of BRCA1 may interact with p53 in breast cancer cells.

Structural Evidence for Direct Interactions between the BRCT Domains of Human BRCA1 and a Phospho-peptide from Human ACC1

The tandem BRCA1 C-terminal (BRCT) domains are phospho-serine/threonine recognition modules essential for the function of BRCA1. Recent studies suggest that acetyl-CoA carboxylase 1 (ACC1), an enzyme with crucial roles in de novo fatty acid biosynthesis and lipogenesis and essential for cancer cell survival, may be a novel binding partner for BRCA1, through interactions with its BRCT domains. We report here the crystal structure at 3.2 A resolution of human BRCA1 BRCT domains in complex with a phospho-peptide from human ACC1 (p-ACC1 peptide, with the sequence 1258-DSPPQ-pS-PTFPEAGH-1271), which provides molecular evidence for direct interactions between BRCA1 and ACC1. The p-ACC1 peptide is bound in an extended conformation, located in a groove between the tandem BRCT domains. There are recognizable and significant structural differences to the binding modes of two other phospho-peptides to these domains, from BACH1 and CtIP, even though they share a conserved pSer-Pro-(Thr/Val)-Phe motif. Our studies establish a framework for understanding the regulation of lipid biosynthesis by BRCA1 through its inhibition of ACC1 activity, which could be a novel tumor suppressor function of BRCA1.

Hymenoic acid, a novel specific inhibitor of human DNA polymerase λ from a fungus of Hymenochaetaceae sp.

Hymenoic acid ( 1) is a natural compound isolated from cultures of a fungus, Hymenochaetaceae sp., and this structure was determined by spectroscopic analyses. Compound 1 is a novel sesquiterpene, trans-4-[(1′ E,5′ S)-5′-carboxy-1′-methyl-1′-hexenyl]cyclohexanecarboxylic acid. This compound selectively inhibited the activity of human DNA polymerase λ (pol λ) in vitro, and 50% inhibition was observed at a concentration of 91.7 μM. Compound 1 did not influence the activities of the other seven mammalian pols (i.e., pols α, γ, δ, ε, η, ι, and κ), but also showed no effect even on the activity of pol β, which is thought to have a very similar three-dimensional structure to the pol β-like region of pol λ. This compound also did not inhibit the activities of prokaryotic pols and other DNA metabolic enzymes tested. These results suggested that compound 1 could be a selective inhibitor of eukaryotic pol λ. This compound had no inhibitory activities against two N-terminal truncated pol λ, del-1 pol λ (lacking nuclear localization signal (NLS), BRCA1 C-terminus (BRCT) domain [residues 133–575]), and del-2 pol λ (lacking NLS, BRCT, domain and proline-rich region [residues 245–575]). The compound 1-induced inhibition of intact pol λ activity was non-competitive with respect to both the DNA template-primer and the dNTP substrate. On the basis of these results, the pol λ inhibitory mechanism of compound 1 is discussed.

A common SNP of MCPH1 is associated with cranial volume variation in Chinese population

Microcephaly (MCPH) genes are informative in understanding the genetics and evolution of human brain volume. MCPH1 and abnormal spindle-like MCPH associated (ASPM) are the two known MCPH causing genes that were suggested undergone recent positive selection in human populations. However, previous studies focusing only on the two tag single nucleotide polymorphisms(SNPs) of MCPH1 and ASPM failed to detect any correlation between gene polymorphisms and variations of brain volume and cognitive abilities. We conducted an association study on eight common SNPs of MCPH1 and ASPM in a Chinese population of 867 unrelated individuals. We demonstrate that a non-synonymous SNP (rs1057090, V761A in BRCA1 C-terminus (BRCT) domain) of MCPH1 other than the two known tag SNPs is significantly associated with cranial volume in Chinese males. The haplotype analysis confirmed the association of rs1057090 with cranial volume, and the homozygote males containing the derived alleles of rs1057090 have larger cranial volumes compared with those containing the ancestral alleles. No recent selection signal can be detected on this SNP, suggesting that the brain volume variation in human populations is likely neutral or under very weak selection in recent human history.

BRCT Domains: phosphopeptide binding and signaling modules

The BRCA1 C-terminus (BRCT) domains are essential for the tumor suppressor function of BRCA1, and have been found in a variety of proteins from bacteria to men. Recent studies demonstrate that the BRCT domain constitutes a novel phosphopeptide binding region. In this review we seek to discuss the recent biochemical and structural data that have helped elucidate the molecular basis of BRCT domain function and BRCT-mediated interactions, with special emphasis on the role of phospho-specific interactions in key networks that regulate DNA repair. Finally we offer predictions on additional phospho-interacting BRCT domains and potential in vivo binding sites for several BRCT domains.