Human RNase III is a 160-kDa protein involved in preribosomal RNA processing

A human RNase III gene encodes a protein of 160 kDa with multiple domains, a proline-rich, a serine- and arginine-rich, and an RNase III domain. The e xpressed purified RNase III domain cleaves double-strand RNA and does not c leave single-strand RNA. The gene is ubiquitously expressed in human tissue s and cell lines, and the protein is localized in the nucleus of the cell, The levels of transcription and translation of the protein do not change du ring different phases of the cell cycle. However, a significant fraction of the protein in the nucleus is translocated to the nucleolus during the S p hase of the cell cycle, That this human RNase III is involved in processing of pre-rRNA, but might cleave at sites different from those described for yeast RNase III, is shown by antisense inhibition of RNase III expression. Inhibition of human RNase III expression causes cell death, suggesting an e ssential role for human RNase III in the cell. The antisense inhibition tec hnique used in this study provides an effective method for functional analy sis of newly identified human genes.