IN VIVO EXCISION OF PYRIMIDINE DIMERS IS MEDIATED BY A DNA N-GLYCOSYLASE IN MICROCOCCUS LUTEUS BUT NOT IN HUMAN FIBROBLASTS |
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Authors: | Michael La Belle Stuart Linn |
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Institution: | Department of Biochemistry, University of California, Berkeley, CA 94720, USA |
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Abstract: | Abstract It has been previously shown that Micrococcus luteus possesses a pyrimidine dimer-specific endonuclease which in vitro , functions as both an endonuclease and DNA-glycosylase. To determine if these combined activities function in vivo , we have isolated and examined the excision products of UV-irradiated M. luteus . In addition, we have devised a procedure to isolate and examine the excision products from UV-irradiated human fibroblasts to determine if an endonuclease/glycosylase activity functions in the excision of UV-induced pyrimidine dimers in human fibroblasts. We find that, in vivo , an endonuclease/glycosylase mechanism is utilized extensively in the repair of pyrimidine dimers by M. luteus , but that human fibroblasts do not appear to use this mechanism. |
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