HIV1 Tat Specific Factor 1 (HTATSF1)

Sequence analysis predicted that the HTATSF1 protein has 754 amino acids. The N-terminal half of HTATSF1 contains 2 RNA-recognition motifs homologous to those in EWS protein and FUS/TLS, while the C-terminal half is rich in acidic amino acids, particularly glutamate and aspartate, and has several potential serine phosphorylation sites. Northern blot analysis revealed expression of a 3.0-kb HTATSF1 transcript in several cell lines. Immunoblot analysis showed that HTATSF1 is expressed as a 140-kD phosphoprotein in numerous cell types, suggesting that HTATSF1 may mediate a broadly active cellular process in addition to its essential role in Tat activation. Binding analysis showed that HTATSF1 weakly associates with TAR RNA. The association with TAR RNA was substantially enhanced by the presence of Tat.