Structural basis to characterise transactivation domain of BRCA1

<p>Familial inheritance of breast and ovarian cancer is attributed to mutations discovered in functional domains of BRCA1 gene. BRCA1 is a multifunctional protein responsible for maintaining the genomic integrity and has transcriptional regulatory function encoded in its C-terminal region. The different amino-terminal e extensions to BRCA1 BRCT domain are responsible for transcription activation. However, only BRCA1 BRCT (1649–1859) amino acids have been explored for its structural characteristics. Noting the importance of extended region to the N-terminus of BRCT different regions of BRCA1 which demonstrates maximum transactivation activity has been explored for their structure and functional activity. Secondary and tertiary structural analysis revealed a limited alpha-helical content with well-folded tertiary structure. <i>In silico</i> tools were used to corroborate the <i>in vitro</i> results. Amino acids composition and sequence analysis display a propensity for intrinsic disorder and coiled-coil formation in BRCA1 (1396–1863) (BRCA1-TAD). The results presented in this paper suggest the extreme flexibility in coiled-coil motif might be an important requirement in the establishment of protein–protein interaction networks for BRCA1.</p

Multimodal approach to explore the pathogenicity of BARD1, ARG 658 CYS, and ILE 738 VAL mutants

<p>BARD1–BRCA1 complex plays an important role in DNA damage repair, apoptosis, chromatin remodeling, and other important processes required for cell survival. BRCA1 and BARD1 heterodimer possess E3 ligase activity and is involved in genome maintenance, by functioning in surveillance for DNA damage, thereby regulating multiple pathways including tumor suppression. BRCT domains are evolutionary conserved domains present in different proteins such as BRCA1, BARD1, XRCC, and MDC1 regulating damage response and cell-cycle control through protein–protein interactions. Nonetheless, the role of BARD1BRCT in the recruitment of DNA repair mechanism and structural integrity with BRCA1 complex is still implicit. To explicate the role of BARD1BRCT in the DNA repair mechanism, in silico, <i>in vitro</i>, and biophysical approach were applied to characterize BARD1 BRCT <i>wild</i>-<i>type</i> and Arg658Cys and Ile738Val mutants. However, no drastic secondary and tertiary structural changes in the mutant proteins were observed. Thermal and chemical denaturation studies revealed that mutants Arg658Cys and Ile738Val have a decrease in <i>T</i>_m and ∆<i>G</i> than the <i>wild type</i>. <i>In silico</i> studies of BARD1 BRCT (568-777) and mutant protein indicate loss in structural compactness on the Ile738Val mutant. Comparative studies of <i>wild</i>-<i>type</i> and mutants will thus be helpful in understanding the basic role of BARD1BRCT in DNA damage repair.</p