endoribonuclease containing an essential RNA component. RNase MRP is a ribonucleoprotein with its RNA component and very likely all of its protein components encoded by nuclear genes. The sequence of the nuclear gene for the RNA component of
RNase MRP has been obtained for vertebrates and fungi for sequence comparisons of earlier reported sequences and the genes are distinctly similar. Inspection
of the coding region and surrounding sequences indicates that it is very
likely that these genes function as polymerase Wpolymerase I11 transcription
units, which may represent an ancient class of nuclear gene.
The genes are single copy in the cases of both mouse and human and it is interesting to note that there is extensive sequence similarity in the 5 -flanking region that surpasses that typical for other small RNA genes of nuclear origin. There are two protein components identified for Saccharomyces cerevisiae RNase MRP: One is shared with
RNase P and the other appears unique to RNase MRP