DNA polymerase zeta （pol ζ） in higher eukaryotes

Most current knowledge about DNA polymerase zeta （pol ζ） comes from studies of the enzyme in the budding yeast Saccharomyces cerevisiae, where pol ζ consists of a complex of the catalytic subunit Rev3 with Rev7, which associates with Revl. Most spontaneous and induced mutagenesis in yeast is dependent on these gene products, and yeast pol can mediate translesion DNA synthesis past some adducts in DNA templates. Study of the homologous gene products in higher eukaryotes is in a relatively early stage, but additional functions for the eukaryotic proteins are already apparent. Suppression of vertebrate REV3L function not only reduces induced point mutagenesis but also causes larger-scale genome instability by raising the frequency of spontaneous chromosome translocations. Disruption of Rev3L function is tolerated in Drosophila, Arabidopsis, and in vertebrate cell lines under some conditions, but is incompatible with mouse embryonic development. Functions for REV3L and REV7（MAD2B） in higher eukaryotes have been suggested not only in translesion DNA synthesis but also in some forms of homologous recombination, repair of interstrand DNA crosslinks, somatic hypermutation of immunoglobulin genes and cell-cycle control. This review discusses recent developments in these areas.

THE EXAMINATION OF AN EBV-DNASE GENE FRAGMENT IN THE PARAFFIN-EMBEDDED NPCI PRECANCEROUS AND FROM HIGHRISK POPULATION NASOPHARYNGEAL TISSUES

Objective: To examine if the EB virus appears innasopharyngeal epithelial cells in the course oftumorigenesis in nasopharyngeal carcinoma (NPC).Methods: Based on the annual investigation of SihuiCounty, a cancer-prevention base of Sun Yat-senUniversity of Medical Sciences(SUMS) and armorHospital out-patient clinic, more than 450 paraffinembedded NPC tissue specimells, precancerous lesionsand precancerosis from a high--risk population werecollected for detection of an EBV-DNase gene fragmentby an optimized PCR method. Results: In 145 of the149 (97.3%) cases with invasive NPC, and 2 of 4 caseswith in situ NPC, only 2 of the 155 subjects withprecancerosis was DNase gene positive, and all 47 casesexamined in the out-patient department of the TumorHospital with precancerous lesions in the nasopharynxwere negative. Conclusion: The universal presence ofan EBV-DNase gene in NPC tissues and the paucity ofEBV-DNase gene in nonmalignant and precancerouslesions in the nasopharynx in a high-risk populationimply that carcinogenesis of NPC occurs before theappearance of EBV in the nasopharynx.

Nontuberculous Mycobacteria Infections in Katavi Rukwa Ecosystems

A study on nontuberculous mycobacteria （NTM） was carried out in wildlife-livestock interface of Katavi Rukwa ecosystem （KRE）. 328 livestock tissues and 178 wild animals were cultured, wild animals were sampled opportunistically during professional hunting and game cropping operations in the KRE protected areas. The objective of the study was to generate data on epidemiology of NTM in the wildlife-livestock interface of the KRE. Methods used to identify the NTM were： culture and isolation, polymerase chain reaction, protein heat shock 65 kilodalton （hsp65） and sequencing. Mycobacteria were detected on 25.9% and 11.9% of livestock and wildlife tissue cultures, respectively. The most NTM isolated were M. kansasii （30%）, M. gastri （30%）, M. fortuitum （1%）, M. intracellulare （4%）, M. indicuspranii （4%）, M. nonchromogenicum （6%） and M. lentiflavum （6%）. Other NTM in smaller percentages were M. hibernae, M. engbaekii, M. septicum, M. arupense and 34.. godii. Due to rise of NTM infection in both human and animals, it is recommended that awareness and laboratory facilities be improved to curb the underreporting especially in TB-endemic countries. For species specific identification, a network of national and regional laboratories is promoted.