BRCA1 splice variants BRCA1a and BRCA1b associate with CBP co-activator.

The second BRCT domain of BRCA1 proteins interacts with p53 and stimulates transcription from the p21WAF1/CIP1 promoter

“…To determine whether intact BRCA1a/1b and a deletion mutant (containing the second BRCT domain aa 1760 ± 1863) bind with p53, in vitro binding was performed with full length wild type human p53 protein. The in vitro translated 35 S-methionine-labeled p53 protein was passed through GST-BRCA1a, GSTBRCA1b, GST-BRCT domain (residues 1760 ± 1863) and a GST control column as described previously (Wang et al, 1997;Cui et al, 1998b). p53 was found to bind speci®cally to GST-BRCA1a, GST-BRCA1b, GST-BRCT domain (residues 1760 ± 1863) but not to GST (Figure 1a, lanes 3, 4 and 5).…”

“…To map the region of p53 which binds to the BRCT domain, a series of p53 deletion mutants expressed as GST fusion proteins (generous gifts from Drs Shenk and Wiman) were incubated with in vitro translated BRCT domain (aa 1760 ± 1863) protein and subjected to GST-pull down assay. The results show that BRCT domain binds to the central region but not to the C-terminal region (amino acids 319 ± 393) (Figure 1b GST, GST-BRCA1a, GST-BRCA1b and GST-BRCT domain (amino acids 1760 ± 1863) proteins were expressed, puri®ed on beads and incubated with in vitro translated 35 S-methioninelabeled p53 and subjected to GST-pull down assay as described a b previously (Wang et al, 1997;Cui et al, 1998b). In lane 1, 1/20th of the in vitro translated protein used for binding was loaded directly.…”

“…Several recent reports have shown moderate homology between the BRCT domains of BRCA1 and the C-terminal region of p53-binding protein (5BP1), the yeast RAD9 protein and multiple proteins involved in cell cycle checkpoint functions responsive to DNA damage (Koonin et al, 1996;Bork et al, 1997;Callebaut and Mornon, 1997). Recently, we and others showed that the N-and C-terminal regions of BRCA1, BRCA1a and BRCA1b proteins activate transcription when fused to GAL4 DNA binding domain (Cui et al, 1998a;Chapman and Verma, 1996;Monteiro et al, 1996), and associate with RNA polymerase II holoenzyme (Scully et al, 1997a) and CBP/P-300 coactivator (Cui et al, 1998b), suggesting a potential role for BRCT domains in the regulation of transcription. The multiple functions of BRCA1 protein(s) include growth/tumor suppression (Holt et al, 1996;Thompson et al, 1995;Rao et al, 1996;Humphrey et al, 1997), induction of apoptosis , cell cycle regulated expression, DNA repair and the maintenance of genomic stability (Lane et al, 1995;Marquis et al, 1995;Scully et al, 1997b;Brugarolas and Jacks, 1997).…”

The BRCA2 is a histone acetyltransferase

“…BRCA1 was also shown to induce apoptosis suggesting that BRCA proteins may play a role in the regulation of apoptosis of cells Rao et al, 1996). It remains to be seen whether BRCA2 plays a similar role in apoptosis.Interestingly, both BRCA1 and BRCA2 gene products are regulated in a cell cycle-dependent manner and have a potential transactivation function (Rajan et al, 1996;' Vaughn et al, 1996;Chapman and Verma, 1996; Monteriro et al, 1996;Milner et al, 1997;Wang et al, 1997;Cui et al, 1998a). Recently, we have shown that BRCA1 proteins interact with transcriptional coactivator CBP suggesting that BRCA1 has a role in the regulation of transcription (Cui et al, 1998b).…”

“…Recently, we have shown that BRCA1 proteins interact with transcriptional coactivator CBP suggesting that BRCA1 has a role in the regulation of transcription (Cui et al, 1998b). Exon 3 of BRCA2 was found to have weak homology with transcriptional factor c-jun and also shown to activate transcription in mammalian cells (Milner et al, 1997).…”