Select members of the bovine pancreatic ribonuclease A (RNase A) superfamily are potent cytotoxins. These cytotoxic ribonucleases enter the cytosol, where they degrade cellular RNA and cause cell death. Ribonuclease inhibitor (RI), a cytosolic protein, binds to members of the RNase A superfamily with inhibition constants that span 10 orders of magnitude. Here, we show that the affinity of a rib...

1. Lysosomal acid RNase was partially purified from a rat liver homogenate and a lysosomal fraction. This RNase, of optimum pH 5 to 6, cleaved RNA to form nucleoside 2’,3’cyclic phosphates, which were hydrolyzed to nucleoside 3’-monophosphates. This enzyme was heat-labile and had a molecular weight of about 24,000 to 28,000, as estimated by gel filtration with Bio-Gel P-60. This lysosomal acid ...

Escherichia coli RNase BN, a member of the RNase Z family of endoribonucleases, differs from other family members in that it also can act as an exoribonuclease in vitro. Here, we examine whether this activity of RNase BN also functions in vivo. Comparison of the X-ray structure of RNase BN with that of Bacillus subtilis RNase Z, which lacks exoribonuclease activity, revealed that RNase BN has a...

Ribonuclease E (RNase E) has a key role in mRNA degradation and the processing of catalytic and structural RNAs in E. coli. We report the discovery of an evolutionarily conserved 17.4 kDa protein, here named RraA (regulator of ribonuclease activity A) that binds to RNase E and inhibits RNase E endonucleolytic cleavages without altering cleavage site specificity or interacting detectably with su...

Ribonuclease L (RNase-L) is an endoribonuclease well known for its roles in innate immunity. Recently it has been shown to regulate several cellular functions by modulating the levels of specific mRNAs. In this study, we investigated whether RNase-L may regulate adipocyte functions. We showed that knockdown of RNase-L reduced 3T3-L1 adipocyte differentiation and lipid accumulation. After mRNA p...

In the presence of Mn2+, reverse transcriptase of both human immunodeficiency virus and murine leukemia virus hydrolyzes duplex RNA. However, designating this novel activity RNase D conflicts with Escherichia coli RNase D, which participates in tRNA processing. On the basis of its location in the RNase H domain, we propose that this novel retroviral activity be redesignated RNase H*.

Here we demonstrate a new regulatory mechanism for tRNA processing in Escherichia coli whereby RNase T and RNase PH, the two primary 3' → 5' exonucleases involved in the final step of 3'-end maturation, compete with poly(A) polymerase I (PAP I) for tRNA precursors in wild-type cells. In the absence of both RNase T and RNase PH, there is a >30-fold increase of PAP I-dependent poly(A) tails that ...

Ribonuclease (RNase) Sa3 is secreted by the Gram-positive bacterium Streptomyces aureofaciens. The enzyme catalyzes the cleavage of RNA on the 3' side of guanosine residues. Here, x-ray diffraction analysis was used to determine the three-dimensional structure of two distinct crystalline forms of RNase Sa3 to a resolution of 2.0 and 1.7 A. These two structures are similar to each other as well ...

The nucleotide sequence analysis of tRNA has required (a) identification of fragments isolated from complete digestion with pancreatic RNase and RNase T1 and, in addition, (b) the analysis of large oligonucleotide fragments produced by partial digestion with RNase T1 (l-4) and, in some cases, partial digestion with pancreatic RNase (5). In continuation of the work reported in the preceding pape...

The endoribonuclease RNase P is involved in the processing of tRNA precursors to generate mature 5' termini. The catalytic activity of RNase P is associated with an RNA, RNase P RNA. A specific interaction between the 3' end of the substrate and RNase P RNA, to form an RNase P RNA-substrate complex, is referred to as the '73-294-interaction'. This interaction has an important role for efficient...