Binding Protein Gene Family Research Articles

Blue-light regulation of transcription for nuclear genes in pea

The expression of many nuclear genes in plants is light regulated. Previous investigations have shown that the excitation of phytochrome can affect transcription rate and steady-state RNA levels for several of these genes. No direct demonstration of the effects of blue light has been reported. We have identified several nuclear genes in pea whose transcription rate and steady-state RNA levels are affected by a single pulse of blue light. Pea seedlings, grown in continuous red light to saturate any phytochrome response, were treated with a single pulse (10(3) mumol.m(-2)) of blue light 6 days after planting. The blue-light treatment resulted in an increase in the steady-state RNA level and rate of transcription for the Cab (chlorophyll a/b binding protein) gene family and a decrease in the steady-state RNA level and the rate of transcription for the gene families corresponding to cDNA clones pEA25 and pEA207. Changes in the rate of transcription for Cab and pEA207 are apparent within 3 hr of the blue-light treatment.

Molecular structure of the chicken vitamin D-induced calbindin-D28K gene reveals eleven exons, six Ca2+-binding domains, and numerous promoter regulatory elements.

The seco-steroid hormone 1,25-dihydroxyvitamin D3 is known to induce the expression of a calcium binding protein termed calbindin-D28K in a variety of target tissues. In order to comprehend the mechanism of induction we have cloned and sequenced the chicken calbindin-D28K gene. The gene spans some 18.5 kilobases (kb) of chromosomal DNA from the putative Cap site to the polyadenylation site of the 2.8 kb mRNA. It is split into 11 coding exons by 10 intervening sequences. The promoter region of this gene is markedly G + C-rich (60-80%) extending from -225 to +400. Within this region we find 70 CpG dinucleotides, four G-C boxes, and numerous known promoter regulatory signals. These putative regulatory signals include a TATA box (ATAAATA) at -30 and a CAT box (CCAAT) at -326. Ten additional variant CAT boxes are found in the upstream promoter region (-218 to -770) of this gene. Furthermore we have identified a glucocorticoid-like responsive element at -410 (TCTACACACTGTTCC) and this element overlaps a metal responsive element (TGCACTC) and a variant CAT box (CCAAAT) and juxtaposes an enhancer-like core element (AAATGGT) on its 3'-side. In addition, the calbindin-D28K promoter is composed of a variety of simple repeated sequences, some of which are components of putative regulatory signals. All splice junctions were found to conform to the GT-AG rule. A consensus sequence of the 5'-splice junction reads AG/GTAAG-TTATA. A consensus sequence of the 3'-splice site consists of two elements: a pyrimidine track (mainly T) followed by ACAG/G-T. A two-dimensional model of calbindin-D28K was constructed which projects the existence of 6 alpha-helix-loop-alpha-helix regions characteristic of calcium binding domains. The 3'-end of the gene consists of a single large (2039 base pair) uninterrupted exon, an organizational feature common to other members of the calcium binding protein gene family which include calmodulin, parvalbumin, Spec I, myosin light chains, etc. Another feature common to the gene family is the presence of the repeated sequence ATTT or TTTA located in the 3'-untranslated exons. These simple repeat sequences could be involved in regulating mRNA degradation by serving as a ribonuclease recognition signal.

Isolation of a rat parvalbumin gene and full length cDNA.

The complete sequence of the rat parvalbumin mRNA was determined by sequencing a near full length cDNA clone and a primer extension product of the 5' untranslated region of this clone. The parvalbumin sequence contained 72 nucleotides of the 5' untranslated region, 333 nucleotides of the coding sequence, and 183 nucleotides of the 3' untranslated sequence in the case of the shorter parvalbumin messenger RNA or 556 nucleotides in the case of the larger parvalbumin messenger RNA. The two RNAs were derived from a single primary transcript since two clones were sequenced which were identical except for the site of polyadenylation. The polyadenylation signal of the shorter, more abundant RNA was AATAAA while the putative signal for the larger RNA was GATAAA. A 32-base pair sequence comprising part of the 5' untranslated region and the first seven codons of the parvalbumin cDNA was 81% homologous to a region of the chicken calmodulin cDNA encoding part of the first Ca2+-binding domain. This homology indicates that this portion of the parvalbumin mRNA may have evolved from a primordial first domain. A parvalbumin genomic clone which hybridized to probes derived from both the coding and 3' untranslated region of the cDNA was cloned from a rat genomic library. Partial sequencing identified an uninterrupted stretch of 585 base pairs identical to the 3' end of the parvalbumin cDNA. Two introns were localized in the genomic clone. Their position with respect to the parvalbumin amino acid sequence corresponded to the intron locations found in genes of several other Ca2+-binding proteins. This result indicates that, despite the deletion of one Ca2+-binding domain, the remainder of the parvalbumin gene has maintained the structural pattern of the Ca2+-binding protein gene family.