Mammalian DNA ligase III: Molecular cloning, chromosomal localization, and expression in spermatocytes undergoing meiotic recombination
- Glaxo Research Inst., Research Triangle Park, NC (United States); and others
Three biochemically distinct DNA ligase activities have been identified in mammalian cell extracts. We have recently purified DNA ligase II and DNA ligase III to near homogeneity from bovine liver and testis tissue, respectively. Amino acid sequencing studies indicated that these enzymes are encoded by the same gene. In the present study, human and murine cDNA clones encoding DNA ligase III were isolated with probes based on the peptide sequences. The human DNA ligase III cDNA encodes a polypeptide of 862 amino acids, whose sequence is more closely related to those of the DNA ligases encoded by poxviruses than to replicative DNA ligases, such as human DNA ligase I. In vitro transcription and translation of the cDNA produced a catalytically active DNA ligase similar in size and substrate specificity to the purified bovine enzyme. The DNA ligase III gene was localized to human chromosome 17, which eliminated this gene as a candidate for the cancer-prone disease Bloom syndrome that is associated with DNA joining abnormalities. DNA ligase III is ubiquitously expressed at low levels, except in the testes, in which the steady-state levels of DNA ligase III mRNA are at least 10-fold higher than those detected in other tissues and cells. Since DNA ligase I mRNA is also present at high levels in the testes, we examined the expression of the DNA ligase genes during spermatogenesis. DNA ligase I mRNA expression correlated with the contribution of proliferating supermatogonia cells to the testes, in agreement with the previously defined role of this enzyme in DNA replications. In contrast, elevated levels of DNA ligase III mRNA were observed in primary supermatocytes undergoing recombination prior to the first meiotic division. Therefore, we suggest that DNA ligase III seals DNA strand breaks that arise during the process of meiotic recombination in germ cells and as a consequence of DNA damage in somatic cells. 62 refs., 7 figs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 379214
- Journal Information:
- Molecular and Cellular Biology, Vol. 15, Issue 10; Other Information: PBD: Oct 1995
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BASIC STUDIES
56 BIOLOGY AND MEDICINE
APPLIED STUDIES
HUMAN CHROMOSOME 17
GENETIC MAPPING
STRAND BREAKS
LIGASES
ENZYME ACTIVITY
AMINO ACID SEQUENCE
GENES
TISSUE DISTRIBUTION
SPERMATOCYTES
MEIOSIS
CELL PROLIFERATION
GENE MUTATIONS
GENE REGULATION
GENE RECOMBINATION
TRANSCRIPTION
SOMATIC CELLS
GENETIC RADIATION EFFECTS
DNA-CLONING
POLYPEPTIDES
HEREDITARY DISEASES
POLYMERASE CHAIN REACTION
DNA HYBRIDIZATION