Search results for "RNase H"

Telomere Length Determines TERRA and R-Loop Regulation through the Cell Cycle

2017

Maintenance of a minimal telomere length is essential to prevent cellular senescence. When critically short telomeres arise in the absence of telomerase, they can be repaired by homology-directed repair (HDR) to prevent premature senescence onset. It is unclear why specifically the shortest telomeres are targeted for HDR. We demonstrate that the non-coding RNA TERRA accumulates as HDR-promoting RNA-DNA hybrids (R-loops) preferentially at very short telomeres. The increased level of TERRA and R-loops, exclusively at short telomeres, is due to a local defect in RNA degradation by the Rat1 and RNase H2 nucleases, respectively. Consequently, the coordination of TERRA degradation with telomere r…

RNase H1 and H2 Are Differentially Regulated to Process RNA-DNA Hybrids

2019

Summary: RNA-DNA hybrids are tightly regulated to ensure genome integrity. The RNase H enzymes RNase H1 and H2 contribute to chromosomal stability through the removal of RNA-DNA hybrids. Loss of RNase H2 function is implicated in human diseases of the nervous system and cancer. To better understand RNA-DNA hybrid dynamics, we focused on elucidating the regulation of the RNase H enzymes themselves. Using yeast as a model system, we demonstrate that RNase H1 and H2 are controlled in different manners. RNase H2 has strict cell cycle requirements, in that it has an essential function in G2/M for both R-loop processing and ribonucleotide excision repair. RNase H1, however, can function independe…

RNase H2 Loss in Murine Astrocytes Results in Cellular Defects Reminiscent of Nucleic Acid-Mediated Autoinflammation

2018

Aicardi-Goutières syndrome (AGS) is a rare early onset childhood encephalopathy caused by persistent neuroinflammation of autoimmune origin. AGS is a genetic disorder and >50% of affected individuals bear hypomorphic mutations in ribonuclease H2 (RNase H2). All available RNase H2 mouse models so far fail to mimic the prominent CNS involvement seen in AGS. To establish a mouse model recapitulating the human disease, we deleted RNase H2 specifically in the brain, the most severely affected organ in AGS. Although RNase H2δGFAPmice lacked the nuclease in astrocytes and a majority of neurons, no disease signs were apparent in these animals. We additionally confirmed these results…

A new method for the mapping of 5' ends of RNAs.

2008

In this article, we describe a new procedure to map 5' ends of RNAs. The procedure consists in the use of specific RNase H digestion of a hybrid formed by the RNA and a complementary DNA oligonucleotide. Northern blot hybridization of the resulting RNA fragment allows an accurate measurement of its length. Although we generally use this procedure as a control of previously performed primer extension analyses, the absence of nonspecific bands, which often occur in primer extensions on RNA templates with extended secondary structures, suggests that our method may be preferable when these difficult templates are analyzed.

Molecular and physiological consequences of faulty eukaryotic ribonucleotide excision repair

2019

Abstract The duplication of the eukaryotic genome is an intricate process that has to be tightly safe‐guarded. One of the most frequently occurring errors during DNA synthesis is the mis‐insertion of a ribonucleotide instead of a deoxyribonucleotide. Ribonucleotide excision repair (RER) is initiated by RNase H2 and results in error‐free removal of such mis‐incorporated ribonucleotides. If left unrepaired, DNA‐embedded ribonucleotides result in a variety of alterations within chromosomal DNA, which ultimately lead to genome instability. Here, we review how genomic ribonucleotides lead to chromosomal aberrations and discuss how the tight regulation of RER timing may be important for preventin…

LEVELS OF RIBONUCLEASE H IN CELLS INFECTED WITH HERPES SIMPLEX VIRUS TYPE1

1981

Ribonuclease H levels in herpes simplex virus-infected cells.

1980

Two forms of ribonuclease H (RNase H) have been identified both in uninfected and Herpes Simplex virus (HSV-)infected BHK cells. Identical RNase H species were detected in control- as well as in infected cells. RNase H I and II have not been found to be associated both with host cell DNA polymerase alpha and beta and HSV-induced DNA polymerase. Infection of BHK cells with HSV type 1 does not lead to a pronounced alteration of RNase H II activity but to an increase (3-fold) of the extractable RNase H I activity. RNase H I activity increases to a maximum between 8-10 hours p.i.; the bulk of HSV-DNA synthesis occurs between 6-8 hours p.i. From these experiments we draw the preliminary conclusi…

Theoretical studies of HIV-1 reverse transcriptase inhibition

2012

Computational methods for accurately calculating the binding affinity of a ligand for a protein play a pivotal role in rational drug design. We herein present a theoretical study of the binding of five different ligands to one of the proteins responsible for the human immunodeficiency virus type 1 (HIV-1) cycle replication; the HIV-1 reverse transcriptase (RT). Two types of approaches are used based on molecular dynamics (MD) simulations within hybrid QM/MM potentials: the alchemical free energy perturbation method, FEP, and the pathway method, in which the ligand is physically pulled away from the binding site, thus rendering a potential of mean force (PMF) for the binding process. Our com…

RNase H1 and H2 are differentially regulated to eliminate RNA-DNA hybrids

2019

SUMMARYRNA-DNA hybrids are tightly regulated to ensure genome integrity. The RNase H enzymes, RNase H1 and H2, contribute to chromosomal stability through the removal of RNA-DNA hybrids. Loss of RNase H2 function is implicated in human diseases of the nervous system and cancer. To better understand RNA-DNA hybrid dynamics, we have focused on elucidating the regulation of the RNase H enzymes themselves. Using yeast as a model system, we demonstrate that RNase H1 and H2 are controlled in different manners. RNase H2 is regulated in a strict cell cycle dependent manner, both in terms of its R-loop removal, and ribonucleotide excision repair functions. RNase H1, however, can function independent…