RNA debranching enzymes are 2′-5′ phosphodiesterases found in all eukaryotes. Their main role is cleavage of intron RNA lariat branch points, promoting RNA turnover via exonucleases. Consistent with this role, cells with reduced RNA debranching enzyme activity accumulate intron RNA lariats. The Saccharomyces cerevisiae RNA debranching enzyme Dbr1p is also a host factor for the yeast long terminal repeat (LTR) retrotransposon Ty1, a model for many aspects of retroviral replication. Fittingly, the human RNA debranching enzyme Dbr1 is a host factor for the human immunodeficiency virus, HIV-1. The yeast and human RNA debranching enzymes act at the reverse transcription stages for Ty1 and HIV-1, respectively. Although efficient production of full-length Ty1 cDNA requires Dbr1p, the findings reported here indicate that production of the earliest distinct cDNA product, minus strand strong stop DNA (–sssDNA), is equivalent in wild type and dbr1∆ mutant cells. Several branched Ty1 RNAs are shown to accumulate in dbr1∆ cells during retrotransposition. These data are consistent with creation of Ty1 RNA branches prior to Ty1 reverse transcription and their removal by Dbr1p to allow efficient extension of early cDNA products. The data support the possibility that RNA branch formation and cleavage play broadly shared, but unknown roles in retroviral and LTR retrotransposon reverse transcription.

RNA脱支酶是在所有真核生物中发现的2'-5'磷酸二酯酶。它们的主要作用是裂解内含子RNA套索分支点，通过核酸外切酶促进RNA转换。与此作用一致，RNA脱支酶活性降低的细胞会积累内含子RNA套索。在酿酒酵母RNA脱支酶Dbr1p也是酵母长末端重复（LTR）逆转座子Ty1（逆转录病毒复制的许多方面的模型）的宿主因子。合适的是，人类RNA脱支酶Dbr1是人类免疫缺陷病毒HIV-1的宿主因子。酵母和人类RNA脱支酶分别在Ty1和HIV-1的逆转录阶段起作用。尽管有效生产全长Ty1 cDNA需要Dbr1p，但此处报道的发现表明，最早的独特cDNA产物负链强终止DNA（–sssDNA）的产生在野生型和dbr1Δ突变细胞中是等效的。多个分支的Ty1 RNA显示在dbr1∆中积累逆转座过程中的细胞。这些数据与在Ty1逆转录之前创建Ty1 RNA分支以及通过Dbr1p去除它们以使早期cDNA产物有效延伸相一致。数据支持RNA分支的形成和裂解广泛共享，但在逆转录病毒和LTR逆转座子逆转录中的作用未知的可能性。