Underwood Dana H, Zinzen Robert P, McEachern Michael J
Department of Genetics, University of Georgia, Athens, GA 30602, USA.
Mol Cell Biol. 2004 Jan;24(2):912-23. doi: 10.1128/MCB.24.2.912-923.2004.
Telomeres are synthesized by telomerase, a specialized reverse transcriptase, which contains a template in its intrinsic RNA component. In Kluyveromyces lactis, the repeats synthesized by the wild-type telomerase are 25 nucleotides (nt) in length and uniform in sequence. To determine the role of the 5-nt repeats defining the ends of the K. lactis telomerase RNA template in telomerase translocation, we have made mutations in and around them and observed their effects on telomere length and the sequence of newly made telomeric repeats. These template mutations typically result in telomeres that are shorter than those of wild-type cells. The mismatches between the telomerase template and the telomeric tip that occur after telomerase-mediated incorporation of the mutations are normally not removed. Instead, the mutations lead to the synthesis of aberrant repeats that range in size from 31 to 13 bp. Therefore, the specificity with which the telomeric tip aligns with the telomere is critical for the production of the uniform repeats seen in K. lactis. In addition, the region immediately 3' of the template may play an important role in translocation of the enzyme.
端粒由端粒酶合成，端粒酶是一种特殊的逆转录酶，其内在RNA成分中含有一个模板。在乳酸克鲁维酵母中，野生型端粒酶合成的重复序列长度为25个核苷酸（nt），且序列一致。为了确定定义乳酸克鲁维酵母端粒酶RNA模板末端的5个核苷酸重复序列在端粒酶易位中的作用，我们对它们及其周围区域进行了突变，并观察了它们对端粒长度和新合成的端粒重复序列的影响。这些模板突变通常会导致端粒比野生型细胞的端粒短。端粒酶介导的突变掺入后，端粒酶模板与端粒末端之间的错配通常不会被消除。相反，这些突变会导致合成大小从31到13 bp不等的异常重复序列。因此，端粒末端与端粒对齐的特异性对于乳酸克鲁维酵母中所见的均匀重复序列的产生至关重要。此外，模板3'端紧邻的区域可能在该酶的易位中起重要作用。
