Expressão heteróloga, purificação e caracterização das proteínas humanas DCRA (Down Syndrome Critical Region Gene A) e DSCR8 (Down Syndrome Critical Region Gene 8).

Abstract

Down syndrome is the most frequent cause of mental retardation affecting millions of people worldwide and results from full or partial trisomy of chromosome 21 (HC21). Rare cases of partial trisomy allowed the identification of a small region in HC21 common to all carriers called Down Syndrome Critical Region. The genes DCRA and DSCR8, mapped to this region, encode two proteins of unknown function. With the aim of contributing to a better characterization of these proteins, DSCR8 was subcloned and expressed in fusion with thiorredoxin in Escherichia coli Rosetta (DE3). Recombinant Trx-DSCR8, observed in the soluble fraction, was subjected to the initial purification assays by affinity chromatography in a Ni-NTA column. The gene DCRA was cloned and expressed in fusion with the proteins thiorredoxin and GFP allowing the partial purification of the protein and the achievement of crystallization and immunological assays. The amino acid sequence of DCRA showed 57% and 49% of identity to a protein of unknown function from Anopheles gambiae and Drosophila melanogaster respectively. Also, in silico analyses revealed that DCRA contains a putative Vps26 domain. Subcellular localization of DCRA in fusion with GFP was observed preferentially in the cytoplasm of the cell lines tested. These results contribute to a better characterization of DCRA and DSCR8 and open up possibilities towards the understanding of the cellular role of these proteins and their relationship with the Down syndrome.