Sewell E, Kinsey J A
Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City 66160, USA.
Mol Gen Genet. 1996 Aug 27;252(1-2):137-45.
Tad is a LINE-like element from Neurospora. Inactive Tad elements have been found in all strains of Neurospora examined; however, active copies of Tad were initially found in a single strain (Adiopodoumé) collected from nature. Active Tad elements can be transferred to laboratory strains by means of crosses, heterokaryons or by transformation with cloned active elements. We have analyzed the pattern of transcripts from Tad elements present in strains derived from Adiopodoumé containing either high or low copy numbers of active Tad. In both kinds of strains we found a complex set of discrete polyadenylated transcripts. As expected, a full-length transcript was detected with 5' and 3' ends that coincide with the consensus 5' and 3' ends of the Tad element. Two additional transcripts with the same polarity as the full-length transcript were identified. One of these plus-strand transcripts is 2.0 kb in length with a 5' end identical to that of the full-length transcript and an internal polyadenylation site. The other (4.2 kb) has an internal start site with termination occurring at the 3' consensus end of the element. The 2.0-kb transcript encodes all of ORF1. The 4.2 kb transcript could encode a 5' truncated version of ORF2. Two minusstrand transcripts were also consistently identified. These represent overlapping transcripts from the 3' tail of Tad. These transcripts share a small intron and 3' polyadenylation site. Their 5' start sites are both internal to the consensus 3' end of Tad. Possible functions of this complex array of transcripts are discussed.
Tad是一种来自粗糙脉孢菌的类LINE元件。在所有检测过的粗糙脉孢菌菌株中都发现了无活性的Tad元件；然而，最初在一株从自然界采集的菌株（阿迪奥波杜梅）中发现了有活性的Tad拷贝。有活性的Tad元件可以通过杂交、异核体或用克隆的活性元件进行转化转移到实验室菌株中。我们分析了来自阿迪奥波杜梅的含有高拷贝数或低拷贝数活性Tad的菌株中Tad元件的转录本模式。在这两种菌株中，我们都发现了一组复杂的离散多聚腺苷酸化转录本。正如预期的那样，检测到了一个全长转录本，其5'端和3'端与Tad元件的共有5'端和3'端一致。还鉴定出另外两个与全长转录本极性相同的转录本。其中一个正链转录本长度为2.0 kb，5'端与全长转录本相同，有一个内部多聚腺苷酸化位点。另一个（4.2 kb）有一个内部起始位点，终止于元件的3'共有末端。2.0 kb的转录本编码了所有的ORF1。4.2 kb的转录本可能编码一个ORF2的5'截短版本。还一致鉴定出了两个负链转录本。这些代表了来自Tad 3'末端的重叠转录本。这些转录本共享一个小内含子和3'多聚腺苷酸化位点。它们的5'起始位点都在Tad共有3'末端内部。讨论了这一复杂转录本阵列可能的功能。
