Characterization of Trypanosoma cruzi High Mobility group B (TcHMGB), a putative chromatin architectural factor

CRIBB P; ALONSO V; PEROZZI M; VILLANOVA GV; TROCHINE A; SERRA E

Mar del Plata

Congreso; IX Congreso Argentino de Protozoología y Enfermedades Parasitarias; 2011

Sociedad Argentina de Protozoología (SAP)

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. Based in homology searches, we identified the coding sequence of TcHMGB, an HMGB family member from Trypanosoma cruzi. TcHMGB has two HMG box domains, like mammalian HMGBs, but lacks the typical C-terminal acidic tail and, instead, bears a 110 aminoterminal domain. The TcHMGB N-terminal domain is conserved between the TriTryp sequences (70-80% similarity) and seems to be unique of kinetoplastid HMGBs. Despite these differences, TcHMGB maintains HMG box architectural functions. We used a recombinant TcHMGB-GST fusion protein in gel shift assays and demonstrated that the trypanosomatid HMGB binds distorted DNA structures like cruciform DNA. This protein is also able to bend linear DNA as determined by T4 ligase circularization assays, like other HMGB family members do. Immunofluorescence and western blot assays, demonstrated that TcHMGB is a nuclear protein expressed in all life cycle stages. The protein content, however, is not constant along the life cycle, being higher in replicative forms than in the infective trypomastigote forms. These differences in TcHMGB levels between life cycle stages may be directly related to the previously described changes in heterochromatin distribution and transcription rates. Together with the already described histone modifications and variant histones accumulation in strand switch regions, where transcription starts or ends, the presence of HMGBs in different genome regions could contribute to the epigenetic control of transcription and other nuclear functions.