Roles of RNase P and Its Subunits

Recent studies show that nuclear RNase P is linked to chromatin structure and function. Thus, variants of this ribonucleoprotein (RNP) complex bind to chromatin of small noncoding RNA genes; integrate into initiation complexes of RNA polymerase (Pol) III; repress histone H3.3 nucleosome deposition; control tRNA and PIWI-interacting RNA (piRNA) gene clusters for genome defense; and respond to Werner syndrome helicase (WRN)-related replication stress and DNA double-strand breaks (DSBs). Likewise, the related RNase MRP and RMRP-TERT (telomerase reverse transcriptase) are implicated in RNA-dependent RNA polymerization for chromatin silencing, whereas the telomerase carries out RNA-dependent DNA polymerization for telomere lengthening. Remarkably, the four RNPs share several protein subunits, including two Alba-like chromatin proteins that possess DEAD-like and ATPase motifs found in chromatin modifiers and remodelers. Based on available data, RNase P and related RNPs act in transition processes of DNA to RNA and vice versa and connect these processes to genome preservation, including replication, DNA repair, and chromatin remodeling. RNase P is a ubiquitous RNP widely known as a tRNA processing endoribonuclease. Recent studies reveal that nuclear RNase P has non-canonical roles in chromatin structure and function. Nuclear RNase P is implicated in noncoding RNA gene transcription by Pol III. RNase P subunits repress histone H3.3 recruitment. In the fruit fly, defective RNase P and tRNA processing lead to replication stress. Human RNase P has a role in DSB repair via HDR. Nuclear RNase P has several related RNPs, that is, RNase MRP, RMRP-TERT, and telomerase, implicated in DNA replication, genome conservation, and chromatin silencing.