2-5A-dependent RNase is the terminal factor in the interferon-regulated 2-5A system thought to function in both the molecular mechanism of interferon action and in the general control of RNA stability. However, direct evidence for specific functions of 2-5A-dependent RNase has been generally lacking. Therefore, we developed a strategy to block the 2-5A system using a truncated form of 2-5A-depe...

A mutant strain deficient in RNase T was isolated and used to study the role of this enzyme in Escherichia coli. Strains lacking as much as 70% of RNase T activity, alone or in combination with the absence of other RNases, display normal growth properties. However, in cca strains, which lack tRNA nucleotidyltransferase, RNase T-deficient derivatives accumulate lower levels of defective tRNA and...

Ribonuclease III (RNase III) represents a family of double-stranded RNA (dsRNA) endonucleases. The simplest bacterial enzyme contains an endonuclease domain (endoND) and a dsRNA binding domain (dsRBD). RNase III can affect RNA structure and gene expression in either of two ways: as a dsRNA-processing enzyme that cleaves dsRNA, or as a dsRNA binding protein that binds but does not cleave dsRNA. ...

Two RNases H of mammalian tissues have been described: RNase HI, the activity of which was found to rise during DNA replication, and RNase HII, which may be involved in transcription. RNase HI is the major mammalian enzyme representing around 85% of the total RNase H activity in the cell. By using highly purified calf thymus RNase HI we identified the sequences of several tryptic peptides. This...

RNase-L mediates critical cellular functions including antiviral, pro-apoptotic, and tumor suppressive activities; accordingly, its expression must be tightly regulated. Little is known about the control of RNASEL expression; therefore, we examined the potential regulatory role of a conserved 3'-untranslated region (3'-UTR) in its mRNA. The 3'-UTR mediated a potent decrease in the stability of ...

RNase R is a processive 3'-5' exoribonuclease with a high degree of conservation in prokaryotes. Although some bacteria possess additional hydrolytic 3'-5' exoribonucleases such as RNase II, RNase R was found to be the only predicted one in the facultative intracellular pathogen Legionella pneumophila. This provided a unique opportunity to study the role of RNase R in the absence of an addition...

Several RNases H1 cleave the RNA-DNA junction of Okazaki fragment-like RNA-DNA/DNA substrate. This activity, termed 3'-junction ribonuclease (3'-JRNase) activity, is different from the 5'-JRNase activity of RNase H2 that cleaves the 5'-side of the ribonucleotide of the RNA-DNA junction and is required to initiate the ribonucleotide excision repair pathway. To examine whether RNase H1 exhibits 3...

A second generation mutant of dimeric human pancreas RNase (HHP2-RNase), was obtained by a single residue mutation (Glu(111)-->Gly) of the previously described dimeric human pancreas RNase variant (HHP-RNase). HHP2-RNase was found to be a highly specific antitumour agent, with an enhanced cytotoxic activity compared with HHP-RNase. The structural and functional requisites of the antitumour acti...

Ribonuclease A (RNase A) is widely used in molecular biology research both for analytical assays and for nucleic acid preparation. The catalytic mechanism of RNase A is well understood and absolutely precludes activity on DNA; however anecdotal reports of DNA degradation by RNase A are not uncommon. Here we describe a mechanism by which RNase A treatment can lead to apparent DNA degradation. Th...

Ribonuclease A (RNase A) and the ribonuclease inhibitor protein (RI) form one of the tightest known protein-protein complexes. RNase A variants and homologues, such as G88R RNase A, that retain ribonucleolytic activity in the presence of RI are toxic to cancer cells. Herein, a new and facile assay is described for measuring the equilibrium dissociation constant (K(d)) and dissociation rate cons...