No abstract

The BRCA1 holoenzyme complex plays an important role in DNA damage repair. ABRAXAS is a newly discovered component of this complex and its Cterminal region directly binds to the BRCA1 BRCT domain. Single crystals of the BRCA1 BRCT-ABRAXAS complex grown by co-crystallization belonged to space group P4 1 2 1 2, with unit-cell parameters a = b = 187.18, c = 85.31 Å . Diffraction data were collected on the BM-14 beamline at the ESRF. Molecularreplacement calculations using Phaser led to three molecules in the asymmetric unit and a high solvent content of 76%.

Signaling through c-Raf downstream pathways is the crucial subject of extensive studies because over expressed or mutated genes in this pathway lead to a variety of human cancers. On the basis of cellular localization, this pathway has been sub-divided into two cascades. The first RAF1-MEK1-ERK2 cascade which remains in the cytosol, whereas the second MEK1-ERK2-RSKs transduces into the nucleus and regulates the transactivation function. But how a few amino acids critically regulate the transcriptional function remains unclear. In this paper, we have performed in silico studies to unravel how atomic complexities at the MEK1-ERK2-RSKs pathways intercedes different functional responses. The secondary structure of the ERK, RSKs have been modeled using Jpred3, PSI-PHRED, protein modeler, and Integrated sequence analyzer from Discovery Studio software. Peptides of RSKs isozymes (RSK1/2/3/4) were built and docked on ERK2 structure using ZDOCK module. The hydropathy index for the RSKs molecules was determined using the KYTE-DOOLITTLE plot. The simulations of complex molecules were carried out using a CHARMM force field. The protein-protein interactions (PPIs) in different cascade of MAP kinase (MAPK) have been shown to be similar to those predicted in vivo. PPIs elucidate that the amino acids located at the conserved domains of MAPK pathways are responsible for transactivation functions.

Germ-line mutations in BRCA 1 (Breast Cancer Susceptibility gene 1) gene have been reported to confer risk of 60-80% for breast cancer and 15-60% for ovarian cancer. Majority of these mutations are found in BRCT and RING domain and BRCA1 association with cancer progression has led to numerous studies investigating the functions of BRCA1 gene and its interacting partners(1). It has been observed that different mutations localized within the BRCT domain are responsible for the pathogenic phenotypes. The BRCT domains are found in proteins involved in DNA damage repair and cell cycle regulations. Protein-Protein Interactions (PPIs) with BRCA1 BRCT and phosphopeptide containing consensus sequences of pS-X-X-F motif promotes trans-activation functions. Small-molecule BRCA1 inhibitors capable of disrupting these BRCT dependent interactions are promising anticancer agents. Therefore, in order to understand PPIs at atomic level, BRCA1 BRCT domain was purified and co-crystallised with small molecule inhibitors(2). The small molecule inhibitors agreeably stained the BRCA1 BRCT crystals. The crystal pictures with the diffractions pattern will be highlighted along with the X-ray diffraction data of co-crystals.