CONICET | Buscador de Institutos y Recursos Humanos

High mobility group B (HMGB) proteins are abundant non-histone chromatin proteins thatplay important roles in the execution and control of many nuclear functions. Based in homologysearches, we identified the coding sequence for the TcHMGB protein, an HMGB family member from Trypanosoma cruzi. TcHMGB has two HMG box domains, like mammalian HMGBs, but lacks the typical C-terminal acidic tail. Instead, it contains a 110 amino acid long N-terminal domain. The TcHMGB amino-terminal domain is conserved between the TriTryp sequences (70-80% similarity) and seems to be characteristic of kinetoplastid HMGBs. Despite these differences, TcHMGB maintains HMG box architectural functions: we demonstrated that the trypanosomatid HMGB binds distorted DNA structures like cruciform DNA in gel shift assays. TcHMGB 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 showed that TcHMGB is a nuclear protein expressed in all life cycle stages. Protein levels, however, seem not to be constant along such life cycle, what may be related to the previously described changes in heterochromatin distribution and transcription rates.