Abstract
A 5'- to 3'-exonuclease of about 45 kDa has been purified from various mammalian sources and shown to be required for the completion of lagging strand synthesis in reconstituted DNA replication systems. RTH1 encodes the yeast Saccharomyces cerevisiae counterpart of the mammalian enzyme. To determine the in vivo biological role of RTH1-encoded 5'- to 3'-exonuclease, we have examined the effects of an rth1 delta mutation on various cellular processes. rth1 delta mutants grow poorly at 30 degrees C, and a cessation in growth occurs upon transfer of the mutant to 37 degrees C. At the restrictive temperature, the rth1 delta mutant exhibits a terminal cell cycle morphology similar to that of mutants defective in DNA replication, and levels of spontaneous mitotic recombination are elevated in the rth1 delta mutant even at the permissive temperature. The rth1 delta mutation does not affect UV or gamma-ray sensitivity but enhances sensitivity to the alkylating agent methyl methanesulfonate. The role of RTH1 in DNA replication and in repair of alkylation damage is discussed.
Highlights
From the Wepartment of Biology and Wepartment of Biophysics, University of Rochester, Rochester, New York 14642 and **Unite de Genetique Moleculaire des Levures
We have determined the in vivo biological role of RTHi by examining the effects of the rth16. mutation on viability, mitotic recombination, and DNA repair
Growth rate is slowed very con iderably in the rthl6. mutant at the permissive temperature, and the rthl6. mutation is inviable at the restrictive temperature of 37°C
Summary
From the Wepartment of Biology and Wepartment of Biophysics, University of Rochester, Rochester, New York 14642 and **Unite de Genetique Moleculaire des Levures To determine the in vivo biological role of RTHl-encoded 5'- to 3'-exonuclease, we have examined the effects of an rthlli. Mutant exhibits a terminal cell cycle morphology similar to that of mutants defective in DNA replication, and levels of spontaneous mitotic recombination are elevated in the rthlli. The role of RTHI in DNA replication and in repair of alkylation damage is discussed. The E. coli poLA exl mutant is defective in 5'- to 3'-exonuclease activity and is temperature-sensitive for growth. II Present address: Sealy Center for Molecular Science, University of Texas Medical Branch, 6.104 Medical Research Bldg., Galveston, TX 77555-1061. H To whom correspondence should be addressed: Sealy Center for Molecular Science, University of Texas Medical Branch, 6.104 Medical Research Bldg., 11th & Mechanic St., Galveston, TX 77555-1061. A 5'- to 3'-exonuclease with a molecular size of
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