Professor
Ph.D., Stanford University, 1983

Program Affiliation: Molecular Biology & Genetics | Microbiology | Plant Biology

Research Groups Affiliation: Cell Biology | Development | Genetics | Genomics & Bioinformatics | Microbiology | Plant Biology

The work in this laboratory focuses on genes whose products are necessary for two fundamental activities of eukaryotes, the detection and repair of DNA damage, and the production of gametes by meiosis. It is known that many of the molecular processes of meiosis echo processes of some kinds of DNA repair: homologous sequences synapse; chromosome breaks are made and repaired; and chromatin structure is altered. Therefore, it is likely that many of the gene products involved in these processes are the same. We study the basidiomycete Coprinus cinereus, in which meiosis is naturally synchronous and meiotic cells are particularly amenable to cytogenetic, molecular, and biochemical analyses.

Genetic analysis revealed four genes, rad3, rad9, rad11, and rad12, which are required for the survival of gamma irradiation and for meiosis, and which are in the same pathway for survival of gamma radiation damage. The rad11 and rad12 genes encode homologs of Mre11 and Rad50, respectively, which are known to be required for DNA double-strand break (DSB) repair and meiosis in diverse organisms. Thus, the rad3-9-11-12 pathway is most likely involved in DSB repair. The rad9 gene encodes a large, proline-rich protein whose homologs in other organisms affect mitotic sister chromatid cohesion and chromatin structure. We have shown that the Rad9 protein is also required for meiotic sister chromatid cohesion and homolog pairing, and that its function in pairing is partially distinct from its role in cohesion.

In a complementary approach to the study of rad genes, we have cloned the gene encoding the C. cinereus homolog of Rad51, a eukaryotic RecA homolog required for the repair of DSBs and for meiosis in all organisms examined. In addition, we have created a dominant selectable marker and used it to generate a collection of tagged meiotic mutants. This collection has so far allowed us to identify and study the C. cinereus homologs of Spo11, a protein required for the initiation of meiotic recombination, and Msh5, which encodes a homolog of the bacterial mismatch repair protein MutS. Current studies in this lab are directed towards an understanding of the role of the rad3-9-11-12 pathway in DSB repair, and the roles of this pathway, spo11, msh5, and related genes in meiotic chromosome structure and function. We have identified eight mutations that suppress the meiotic defects of the spo11 mutant, and we have recently found that the C. cinereus msh5 gene is required for pre-meiotic DNA replication. We have confirmed that mutations affecting the ATP binding domain of Rad50 cause defects in meiotic chromosome synapsis, and, importantly, we found that a mutation affecting the second coiled-coil region of Rad50 leads to an almost complete absence of meiotic chromosome condensation and synapsis; this is the first evidence that this region is critical for meiotic chromosome function.

We have recently initiated studies of expressed sequence tags (ESTs) from meiotic cells, and microarray analysis of gene expression during meiosis and DNA repair. A C. cinereus genome sequencing project will likely be underway in the near future, which will make this organism an even more powerful system for the analysis of DNA repair and meiosis.

Casselton, L. A. and M. E. Zolan. 2002. The art and design of genetic screens: filamentous fungi. Nature Reviews Genetics 3, 683 - 697.

Gerecke, E. E. and M. E. Zolan. 2000. An mre11 mutant of Coprinus cinereus has defects in meiotic chromosome pairing, condensation and synapsis. Genetics 154: 1125-1139.

Celerin M., S. T. Merino, J. E. Stone, A, M. Menzie, M. E. Zolan. 2000. Multiple roles of Spo11 in meiotic chromosome behavior. EMBO J 19: 2739-2750.

Merino, S. T., W. J. Cummings, S. N. Acharya, M. Celerin and M. E. Zolan. 2000. Replication dependent early meiotic requirement for Spo11 and Rad50. Proc. Natl. Acad. Sci. USA 97: 10477-10482.

Li, Libo, E. E. Gerecke and M. E. Zolan. 1999. Homolog pairing and meiotic progression in Coprinus cinereus. Chromosoma 108: 384-392.

Cummings, W. J., M. Celerin, J. Crodian, L. Brunick and M. E. Zolan. 1999. Insertional mutagenesis in Coprinus cinereus: use of a dominant selectable marker to generate tagged, sporulation-defective mutants. Current Genetics 36: 371-382.

Yeager Stassen, N., J. M. Logsdon, Jr., G. J. Vora, H. H. Offenberg, J. D. Palmer and M. E. Zolan. 1997. Isolation and characterization of rad51 orthologs from Coprinus cinereus and Lycopersicon esculentum, and phylogenetic analysis of eukaryotic recA homologs. Current Genetics 31: 144-157.

Seitz, L.C., K. Tang, W.J. Cummings and M.E. Zolan. 1996. The rad9 gene of Coprinus cinereus encodes a proline-rich protein required for meiotic chromosome condensation and synapsis. Genetics 142: 1105-1117.

Ramesh, M.A. and M.E. Zolan. 1995. Chromosome dynamics in rad12 mutants of Coprinus cinereus. Chromosoma 104: I89-202.