Functional characterisation of a novel nuclear protein, Hcc-1

Abstract

Hcc-1 is a novel nuclear protein containing the SAP DNA binding domain. We have shown that Hcc-1 binds to both double-stranded and single-stranded DNA with higher affinity for single-stranded DNA. In addition, it is also shown to bind specifically to scaffold/matrix attachment region (S/MAR) DNA. This nucleic acid binding characteristic suggests a potential function of Hcc-1 as a heterogeneous ribonucleoprotein complex. Using a yeast two-hybrid screen, we have identified two DEAD-box RNA helicase proteins, BAT1 and DDX39, as interacting proteins with Hcc-1. The interactions with these RNA helicases point to a function of Hcc-1 in RNA biogenesis such as the spliceosome assembly. Furthermore, overexpression of Hcc-1 in HEK293 cell line showed a significant slower growth rate (p = 0.0173 compared to controls) and accumulations of cells (p = 0.0276 compared to HEK293 cells) at the G2/M phase of the cell cycle. Interestingly, the interacting protein, BAT1 was also implicated in growth inhibition. Taken together, these findings propose potential roles for Hcc-1 in growth regulation and RNA metabolism.