Bibbins M, Cummings N J, Connerton I F
Department of Food Macromolecular Science, Institute of Food Research, Reading, UK.
Mol Gen Genet. 1998 May;258(4):431-6. doi: 10.1007/s004380050752.
A repeated DNA sequence in the genome of Neurospora crassa has been identified as a family of degenerate retroelements. Retroelements encode protein sequences with clear homology to the reverse transcriptase, RNase H and endonuclease products of the pol genes common to retroviruses and retrotransposons. These sequence comparisons place the N. crassa element within the gypsy group of retrotransposons, akin to other elements found in filamentous fungi. However, the Neurospora element is defective, as no flanking long terminal repeats (LTRs) could be distinguished and the pol gene homologues contain numerous stop codons as a result of multiple base substitutions. The base composition of the element displays significant under-representation of the dinucleotide CpA, the preferred target site of repeat-induced point mutation (RIP). The genomic sequences exhibit G:C to A:T transitions between copies which are diagnostic of RIP. The degenerate retroelement has accordingly been designated by the acronym dab-1 (dead and buried).
粗糙脉孢菌基因组中的一个重复DNA序列已被鉴定为一个退化逆转录元件家族。逆转录元件编码的蛋白质序列与逆转录病毒和逆转座子共有的pol基因的逆转录酶、核糖核酸酶H和内切核酸酶产物具有明显的同源性。这些序列比较将粗糙脉孢菌元件置于逆转座子的吉普赛组中，类似于在丝状真菌中发现的其他元件。然而，粗糙脉孢菌元件是有缺陷的，因为无法区分侧翼长末端重复序列（LTR），并且由于多个碱基替换，pol基因同源物包含许多终止密码子。该元件的碱基组成显示二核苷酸CpA的显著低丰度，而CpA是重复诱导点突变（RIP）的首选靶位点。基因组序列在拷贝之间表现出G:C到A:T的转换，这是RIP的诊断特征。因此，这个退化逆转录元件被简称为dab-1（死亡与埋葬）。
