Homo-oligomerization Is the Essential Function of the Tandem BRCT Domains in the Checkpoint Protein Crb2

Li-Lin Du,Bettina A Moser,Paul Russell

doi:10.1074/jbc.m403326200

Li-Lin Du, Bettina A Moser + Show 1 more

Open Access

https://doi.org/10.1074/jbc.m403326200

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Abstract

BRCT (BRCA1 C terminus) domains are frequently found as a tandem repeat in proteins involved in DNA damage responses, such as Saccharomyces cerevisiae Rad9, human 53BP1 and BRCA1. Tandem BRCT domains mediate protein-protein and protein-DNA interactions. However, the functional significance of these interactions is largely unknown. Here we report the oligomerization of Schizosaccharomyces pombe checkpoint protein Crb2 through its tandem BRCT domains. Truncated Crb2 without BRCT domains is defective in DNA damage checkpoint signaling. However, addition of either of two heterologous dimerization motifs largely restores the functions of truncated Crb2 without BRCT domains. Replacement of Crb2 BRCT domains with a dimerization motif also renders cells resistant to the dominant negative effect of overexpressing Crb2 BRCT domains. These results demonstrate that the crucial function of the tandem BRCT domains is to oligomerize Crb2.

Highlights

Protein interactions, BRCT domains have been shown to bind broken DNA ends (12, 13)
Replacement of Crb[2] BRCT domains with a dimerization motif renders cells resistant to the dominant negative effect of overexpressing Crb[2] BRCT domains. These results demonstrate that the crucial function of the tandem BRCT domains is to oligomerize Crb[2]
We have recently shown that large scale recruitment of Crb[2] to sites of DNA damage requires its association with histone H2A that has been phosphorylated at its C terminus by Rad[3] and Tel[1], the fission yeast homologs of ATR and ATM, respectively (23)

Summary

Introduction

Protein interactions, BRCT domains have been shown to bind broken DNA ends (12, 13). We report the oligomerization of Schizosaccharomyces pombe checkpoint protein Crb[2] through its tandem BRCT domains. We show that a heterologous dimerization motif can effectively substitute for the tandem BRCT domains in Crb[2], demonstrating that the crucial function of the BRCT domains is to mediate a Crb2-Crb[2] interaction.

Results

Conclusion