NMR Structure of the N-terminal Domain of Saccharomyces cerevisiae RNase HI
Reveals a Fold with a Strong Resemblance to the N-terminal Domain of Ribosomal
Protein L9

A Chain A, N-Terminal Domain Of Saccharomyces Cerevisiae Rnase Hi Reveals A Fold With A Resemblance To The N-Terminal Domain Of Ribosomal Protein L9

NMR Structure of the N-terminal Domain of Saccharomyces cerevisiae RNase HI
Reveals a Fold with a Strong Resemblance to the N-terminal Domain of Ribosomal
Protein L

Eukaryotic ribonucleases H of known sequence are composed of an RNase H domain
similar in size and sequence to that of Escherichia coli RNase HI and
additional domains of unknown function. The RNase H1 of Saccharomyces
cerevisiae has such an RNase H domain at its C-terminus. Here we show that the
N-terminal non-RNase H portion of the yeast RNase H1 binds tightly to
double-stranded RNA (dsRNA) and RNA-DNA hybrids even in the absence of the
RNase H domain. Two copies of a sequence with limited similarity to the
dsRNA-binding motif are present in this N-terminus. When the first of these
sequences is altered, the protein no longer binds tightly to dsRNA and exhibits
an increase in RNase H activity. Unlike other dsRNA-binding proteins,
increasing the Mg2+ concentration from 0.5 mM to 5 mM inhibits binding of RNase
H1 to dsRNA; yet a protein missing the RNase H domain binds strongly to dsRNA
even at the higher Mg2+ concentration. These results suggest that binding to
dsRNA and RNase H activity are mutually exclusive, and the Mg2+ concentration
is critical for switching between the activities. Changes in the Mg2+
concentration or proteolytic severing of the dsRNA-binding domain could alter
the activity or location of the RNase H and may govern access of the enzyme to
the substrate. Sequences similar to the dsRNA-binding motif are present in
other eukaryotic RNases H and the transactivating protein of cauliflower mosaic
virus, suggesting that these proteins may also bind to dsRNA.

The non-RNase H domain of Saccharomyces cerevisiae RNase H1 binds double-stranded RNA: magnesium modulates the switch between double-stranded RNA binding and RNase H activity.

We have cloned genes encoding RNase H from Escherichia coli rnh mutants,
Salmonella typhimurium and Saccharomyces cerevisiae. Selection was accomplished
by suppression of the temperature-sensitive growth phenotype of Escherichia
coli strains containing the rnh-339::cat and either recB270 (Ts) or recC271
(Ts) mutations. RNases H from E. coli and S. typhimurium contained 155 amino
acid residues and differed at only 11 positions. The S. cerevisiae and E. coli
RNases H were about 30% homologous. A comparison of the amino acid sequences of
several RNases H from cellular and retroviral sources revealed some strongly
conserved regions as well as variable regions; the carboxyl-terminus was
particularly variable. The overlapping, divergent promoter gene organization
found in E. coli was observed to be present in S. typhimurium.

Selective cloning of genes encoding RNase H from Salmonella typhimurium, Saccharomyces cerevisiae and Escherichia coli rnh mutant.

N-Terminal Domain Of Saccharomyces Cerevisiae Rnase Hi Reveals A Fold With A Resemblance To The N-Terminal Domain Of Ribosomal

K7_Rnh1p [Saccharomyces cerevisiae Kyokai no. 7]

Rnh1p [Saccharomyces cerevisiae YJM1078]

RecName: Full=Ribonuclease H; Short=RNase H

TPA: Rnh1p [Saccharomyces cerevisiae S288c]

DISTANCE GEOMETRY AND SIMULATED ANNEALING