c. elegans germ cells show temperature and age-dependent expression of cer1, a gypsyty3-related retrotransposon秀丽隐杆线虫生殖细胞显示温度和年龄相关性cer1的表达,一个gypsyty3-related逆转录转座子.pdfVIP

C. elegans Germ Cells Show Temperature and Age- Dependent Expression of Cer1, a Gypsy/Ty3-Related Retrotransposon Shannon Dennis1,2,3, Ujwal Sheth1,2., Jessica L. Feldman1,2., Kathryn A. English1,2, James R. Priess1,2,3* 1 Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America, 2 Howard Hughes Medical Institute, Seattle, Washington, United States of America, 3 Molecular and Cellular Biology Program, University of Washington, Seattle, Washington, United States of America Abstract Virus-like particles (VLPs) have not been observed in Caenorhabditis germ cells, although nematode genomes contain low numbers of retrotransposon and retroviral sequences. We used electron microscopy to search for VLPs in various wild strains of Caenorhabditis, and observed very rare candidate VLPs in some strains, including the standard laboratory strain of C. elegans, N2. We identified the N2 VLPs as capsids produced by Cer1, a retrotransposon in the Gypsy/Ty3 family of retroviruses/retrotransposons. Cer1 expression is age and temperature dependent, with abundant expression at 15uC and no detectable expression at 25uC, explaining how VLPs escaped detection in previous studies. Similar age and temperature- dependent expression of Cer1 retrotransposons was observed for several other wild strains, indicating that these properties are common, if not integral, features of this retroelement. Retrotransposons, in contrast to DNA transposons, have a cytoplasmic stage in replication, and those that infect non-dividing cells must pass their genomic material through nuclear pores. In most C. elegans germ cells, nuclear pores are largely covered by germline-specific organelles called P granules. Our results suggest that Cer1 capsids target meiotic germ cells exiting pachytene, when free nuclear pores are added to the nucl