Trypanosoma cruzi “HIGH MOBILITY GROUP B” PROTEIN IS A CHROMATIN ARCHITECTURAL FACTOR

CRIBB P.; PEROZZI M; VILLANOVA GV; SERRA EC

Puerto Madryn

Congreso; 46° Reunión Anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular.; 2010

SAIB

High mobility group B (HMGB) proteins are abundant non-histone chromatin proteins that play important roles in the execution and control of many nuclear functions. TcHMGB is an HMGB family member from Trypanosoma cruzi, the causative agent of Chagas´ disease. TcHMGB has two HMG box domains, like mammalian HMGBs, but lacks the typical C-terminal acidic tail and, instead, bears a 110 amino-terminal domain that seems to be unique of kinetoplastid HMGBs. Besides these differences, TcHMGB maintains HMG box architectural functions: it binds distorted DNA structures like cruciform DNA and it is also able to bend linear DNA. TcHMGB is present in the nucleus in all life cycle stages. The protein content, however, is not constant, being higher in replicative forms (amastigotes and epimastigotes) than in the non replicative trypomastigote form. This is consistent with the lower heterochromatin content and higher transcription rates previously reported in replicative forms. In contrast to H1 histone, HMGB proteins cause chromatin to be more relaxed, and concomitantly more accessible to transcription factors, chromatin remodeling complexes and other nuclear proteins. In this context, TcHMGB may alter chromatin structure between life cycle stages, but also in different genome regions, taking part in epigenetic control of nuclear processes like transcription, recombination, replication and repair.