Forney J D, Blackburn E H
Department of Molecular Biology, University of California, Berkeley 94720.
Mol Cell Biol. 1988 Jan;8(1):251-8. doi: 10.1128/mcb.8.1.251-258.1988.
We analyzed sites of macronuclear telomere addition at a single genetic locus in Paramecium tetraurelia. We showed that in homozygous wild-type cells, differential genomic processing during macronuclear development resulted in the A surface antigen gene being located 8, 13, or 26 kilobases upstream from a macronuclear telomere. We describe variable rearrangements that occurred at the telomere 8 kilobases from the A gene. A mutant (d48) that forms a telomere near the 5' end of the A gene was also analyzed. This mutant was shown to create simple terminal deletions; telomeric repeats were added directly to the truncated wild-type A gene sequence. In both the mutant and wild-type cells, the telomeric sequences (a mixture of C4A2 and C3A3 repeats) were added to various sequences within a specific 200- to 500-base-pair region rather than to a single site. No similarities were found in the primary sequences surrounding the telomere addition sites. The mutation in d48 changed the region of telomere addition at the A gene locus; this is the first example in ciliates of a mutation that affects the site of telomere addition.
我们分析了四膜虫大核端粒添加在单个基因位点的情况。我们发现，在纯合野生型细胞中，大核发育过程中的差异基因组加工导致A表面抗原基因位于大核端粒上游8、13或26千碱基处。我们描述了在距离A基因8千碱基的端粒处发生的可变重排。还分析了一个在A基因5'端附近形成端粒的突变体（d48）。该突变体被证明会产生简单的末端缺失；端粒重复序列直接添加到截短的野生型A基因序列上。在突变体和野生型细胞中，端粒序列（C4A2和C3A3重复序列的混合物）被添加到特定200至500碱基对区域内的各种序列上，而不是添加到单个位点。在端粒添加位点周围的一级序列中未发现相似性。d48中的突变改变了A基因位点的端粒添加区域；这是纤毛虫中影响端粒添加位点的突变的首个例子。
