Amplified RNase H activity in Escherichia coli B/r increases sensitivity to ultraviolet radiation

Journal Article · Thu Jan 01 04:00:00 EST 1987 · Genetics; (United States)

OSTI ID:6637244

Bockrath, R; Wolff, L; Farr, A; Crouch, R J

Strains of E. coli B/r transformed with the plasmid pSK760 were found to be sensitized to inactivation by ultraviolet radiation (UV) and to have elevated levels of RNase H activity. Strains transformed with the carrier vector pBR322 or the plasmid pSK762C derived from pSK760 but with an inactivated rnh gene were not sensitized. UV-inactivation data for strains having known defects in DNA repair and transformed with pSK760 suggested an interference by RNase H of postreplication repair: uvrA cells were strongly sensitized, wild-type and uvrA recF cells were moderately sensitized and recA cells were not sensitized; and minimal medium recovery was no longer apparent in sensitized uvrA cells. Biochemical studies showed that post-UV DNA synthesis was sensitized and that the smaller amounts of DNA synthesized after irradiation, while of normal reduced size as indicated by sedimentation position in alkaline sucrose gradients, did not shift to a larger size (more rapidly sedimenting) upon additional incubation. The authors suggest an excess level of RNase H interferes with reinitiation of DNA synthesis on damage templates to disturb the normal pattern of daughter strand gaps and thereby to inhibit postreplication repair.

• Research Organization: Indiana Univ. School of Medicine, Indianapolis
• OSTI ID: 6637244
• Journal Information: Genetics; (United States), Journal Name: Genetics; (United States) Vol. 115:1; ISSN GENTA
• Country of Publication: United States
• Language: English

Related Subjects

560130* -- Radiation Effects on Microorganisms
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BACTERIA
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CELL CONSTITUENTS
DNA REPAIR
ELECTROMAGNETIC RADIATION
ENZYME ACTIVITY
ENZYMES
ESCHERICHIA COLI
ESTERASES
GENES
HYDROLASES
INHIBITION
MICROORGANISMS
PHOSPHODIESTERASES
PLASMIDS
RADIATIONS
RADIOSENSITIVITY
RECOVERY
REPAIR
RNA-ASE
ULTRAVIOLET RADIATION