BCL6 (B-Cell Lymphoma 6)

3q27.3

706 amino acids; composed of a NH2-term BTB/POZ domain (amino acids 1-130 (32-99 according to Swiss-Prot) which mediates homodimerization and protein-protein interactions with other corepressors (including HDAC1 and NCOR2/SMRT to constitute a large repressing complex, another transcription repression domain (191-386), PEST sequences (300-417) with a KKYK motif (375-379), and six zinc finger at the C-term (518-541, 546-568, 574-596, 602-624, 630-652, 658-681), responsible for sequence specific DNA binding. Transcription repressor; recognizes the consensus sequence: TTCCT(A/C)GAA (Albagli-Curiel, 2003). Role in germinal centers of lymphoid follicles. BCL6 prevents ATM and TP53 to induce apoptosis in response to DNA rearrangements such as somatic hypermutation and class switch recombination. Therefore essential for normal B cell development.

HSP90AA1 (heat shock protein 90 alpha family class A member 1)

14q32.31

HSP90AA1 is also known as HSP90. Molecular chaperone. Possesses an ATP binding site with intrinsic ATPase activity that regulates its conformation. Promotes the maturation, structural maintenance and regulation of specific target proteins called client proteins. Maintains protein homeostasis. HSP90AA1/HSP90 interacts with regions of client proteins where protein folding clefts merge. Folding clefts are a general topological feature of proteins in native conformation, and many of these hydrophobic clefts, must open to permit access of ligands. HSP90AA1/HSP90 stabilizes the open cleft, impeding further unfolding and Hsp70-dependent ubiquitination (Pratt et al., 2010). HSP90AA1/HSP90 and its associated co-chaperones facilitate a precise and efficient working environment beneficial for telomere function (DeZwaan and Freeman, 2010). HSP90AA1/HSP90 is exploited by cancer cells to support the activated and/or metastable forms of oncoproteins, and to buffer cellular stresses induced by the malignancy. Hsp90 is often overexpressed in cancer cells (Neckers and Workman, 2012).