B-cell lymphoma 6 protein is a protein that in humans is encoded by the BCL6gene.[1] Like BCL2, BCL3, BCL5, BCL7A, BCL9 and BCL10, it has clinical significance in lymphoma.
The protein encoded by this gene is an evolutionarily conserved zinc finger transcription factor and contains an N-terminal POZ/BTB domain. This protein acts as a sequence-specific repressor of transcription and has been shown to modulate the STAT-dependent Interleukin 4 (IL-4) responses of B cells. This protein can interact with several corepressor complexes to inhibit transcription. This gene is found to be frequently translocated and hypermutated in diffuse large B cell lymphoma (DLBCL)[2][3][4] and contributes to the pathogenesis of DLBCL. An exon 7 skipping splice variant encodes a shorter form of the protein which lacks the first two zinc fingers of the DNA binding domain.[5]
Physiologically, BCL6 is a master transcription factor which leads the differentiation of naive helper T cells in Follicular Helper T cells (TFH cells).[6] Its action is negatively regulated by the gene PRDM1 encoding the transcription factor Blimp-1.[7]
Diagnostic utility
The presence of BCL6 can be demonstrated in tissue sections using immunohistochemistry. It is exclusively present in the B-cells of both healthy and neoplasticgerminal centres. It therefore demonstrates both reactive hyperplasia in lymph nodes and a range of lymphomas derived from follicular B-cells, such as Burkitt's lymphoma, follicular lymphoma and the nodular lymphocyte predominant subtype of Hodgkin's disease. It is often used together with antibodies to Bcl-2 antigen to distinguish neoplastic follicles from those found in benign hyperplasia, for which Bcl-2 is negative.[8]
↑Leong, Anthony S-Y; Cooper, Kumarason; Leong, F Joel W-M (2003). Manual of Diagnostic Cytology (2nd ed.). Greenwich Medical Media, Ltd. p. 29. ISBN1-84110-100-1.
↑Vasanwala FH, Kusam S, Toney LM, Dent AL (August 2002). "Repression of AP-1 function: a mechanism for the regulation of Blimp-1 expression and B lymphocyte differentiation by the B cell lymphoma-6 protooncogene". Journal of Immunology. 169 (4): 1922–9. doi:10.4049/jimmunol.169.4.1922. PMID12165517.
↑ 11.011.1David G, Alland L, Hong SH, Wong CW, DePinho RA, Dejean A (May 1998). "Histone deacetylase associated with mSin3A mediates repression by the acute promyelocytic leukemia-associated PLZF protein". Oncogene. 16 (19): 2549–56. doi:10.1038/sj.onc.1202043. PMID9627120.
↑ 15.015.1Wong CW, Privalsky ML (October 1998). "Components of the SMRT corepressor complex exhibit distinctive interactions with the POZ domain oncoproteins PLZF, PLZF-RARalpha, and BCL-6". The Journal of Biological Chemistry. 273 (42): 27695–702. doi:10.1074/jbc.273.42.27695. PMID9765306.
↑Davies JM, Hawe N, Kabarowski J, Huang QH, Zhu J, Brand NJ, Leprince D, Dhordain P, Cook M, Morriss-Kay G, Zelent A (January 1999). "Novel BTB/POZ domain zinc-finger protein, LRF, is a potential target of the LAZ-3/BCL-6 oncogene". Oncogene. 18 (2): 365–75. doi:10.1038/sj.onc.1202332. PMID9927193.
↑Dhordain P, Albagli O, Honore N, Guidez F, Lantoine D, Schmid M, The HD, Zelent A, Koken MH (December 2000). "Colocalization and heteromerization between the two human oncogene POZ/zinc finger proteins, LAZ3 (BCL6) and PLZF". Oncogene. 19 (54): 6240–50. doi:10.1038/sj.onc.1203976. PMID11175338.
Further reading
Ueda C, Akasaka T, Ohno H (July 2002). "Non-immunoglobulin/BCL6 gene fusion in diffuse large B-cell lymphoma: prognostic implications". Leukemia & Lymphoma. 43 (7): 1375–81. doi:10.1080/10428190290033305. PMID12389616.
Niu H (December 2002). "The proto-oncogene BCL-6 in normal and malignant B cell development". Hematological Oncology. 20 (4): 155–66. doi:10.1002/hon.689. PMID12469325.
Tokuhisa T (December 2002). "[A role for Bcl6 in immune memory development]". Tanpakushitsu Kakusan Koso. Protein, Nucleic Acid, Enzyme. 47 (16 Suppl): 2306–12. PMID12518453.
Ohno H (April 2004). "Pathogenetic role of BCL6 translocation in B-cell non-Hodgkin's lymphoma". Histology and Histopathology. 19 (2): 637–50. PMID15024721.
Pasqualucci L, Bereshchenko O, Bereschenko O, Niu H, Klein U, Basso K, Guglielmino R, Cattoretti G, Dalla-Favera R (2004). "Molecular pathogenesis of non-Hodgkin's lymphoma: the role of Bcl-6". Leukemia & Lymphoma. 44 Suppl 3: S5–12. doi:10.1080/10428190310001621588. PMID15202519.
Jardin F, Ruminy P, Bastard C, Tilly H (February 2007). "The BCL6 proto-oncogene: a leading role during germinal center development and lymphomagenesis". Pathologie-Biologie. 55 (1): 73–83. doi:10.1016/j.patbio.2006.04.001. PMID16815642.