Current Genetics

, Volume 25, Issue 2, pp 142–149

Analysis of the role of the NUC1 endo/exonuclease in yeast mitochondrial DNA recombination

  • Hans Peter Zassenhaus
  • Grace Denniger
Original Articles

DOI: 10.1007/BF00309540

Cite this article as:
Zassenhaus, H.P. & Denniger, G. Curr Genet (1994) 25: 142. doi:10.1007/BF00309540


Mitochondrial DNA recombination was reduced in an yeast mutant lacking the NUC1 endo/exonuclease. Between linked markers in either the ω or cob region the frequency of recombination decreased nearly 50% compared to wild-type. Gene conversion frequencies in the var1 gene and in the ω region were also lower in the mutant strain. In particular, the gradient of gene conversion at ω was most affected by the absence of the NUC1 nuclease. In crosses between nuclease-deficient and wild-type strains, gene conversion frequencies at ω were reduced only when the ω+ allele was contributed to the zygote by the nuclease-deficient parent. We propose that the 5′ exonuclease activity of the NUC1 nuclease functions during recombination to enlarge heteroduplex tracts following a double-strand break in DNA. In crosses between nuclease-deficient and wild-type strains, the anisotropy in gene conversion frequencies at ω is hypothesized to be due to the slow mixing of parental motochondrial membranes as they fuse in the zygote.

Key words

YeastMitochondriaDNA recombination5′ exonuclease

Copyright information

© Springer-Verlag 1994

Authors and Affiliations

  • Hans Peter Zassenhaus
    • 1
  • Grace Denniger
    • 1
  1. 1.Department of Molecular Microbiology and ImmunologySt. Louis University Medical CenterSt. LouisUSA