Phospholipase Cβ1 is Linked to RNA interference of Specific Genes through Translin‐Associated Factor X

Abstract

Phospholipase Cβ1 (PLCβ1) is a G protein regulated enzyme whose activity results in proliferative and mitogenic changes in the cell. We have found that PLCβ1 binds to the RNA processing protein Translin‐Associated factor X (TRAX) and that this binding competes with G proteins. Here, we show that endogenous PLCβ1 and TRAX interact in SK‐N‐SH cells and in HEK293 cells. In HEK293 cells, TRAX over‐expression ablates Ca2+ signals generated by G protein‐PLCâ1 activation. TRAX plays a key role in protein down‐regulation by small, interfering RNA. PLCβ1 overexpression completely reverses down‐regulation of GAPDH by siRNA in HEK293 and HeLa cells as seen by recovery in both the transcript and protein levels. Also, down‐regulation of endogenous PLCβ1 in HEK293 and HeLa cells increases siRNA(GAPDH) silencing. While PLCβ1 overexpression reverses cell death caused by siRNA(LDH), it does not affect cell survival or silencing of other genes (e.g. cyclophilin, Hsp90, translin). PLCβ1 overexpression in HEK293 and HeLa cells reduces the total amount of small RNAs. LDH and GAPDH are part of a complex that promotes H2B synthesis allowing progression through the S phase. We find PLCβ1 reverses the cell death and completely rescues H2B levels caused by siRNA knock‐down of LDH or GAPDH. Taken together, our study shows a novel role of PLCβ1 in gene regulation through TRAX association. Support‐NIH GM053132.