Institut Pasteur, Unité des Aspergillus, Département Parasitologie et Mycologie, Paris, France.
PLoS Genet. 2013;9(8):e1003686. doi: 10.1371/journal.pgen.1003686. Epub 2013 Aug 15.
Most Cryptococccus neoformans genes are interrupted by introns, and alternative splicing occurs very often. In this study, we examined the influence of introns on C. neoformans gene expression. For most tested genes, elimination of introns greatly reduces mRNA accumulation. Strikingly, the number and the position of introns modulate the gene expression level in a cumulative manner. A screen for mutant strains able to express functionally an intronless allele revealed that the nuclear poly(A) binding protein Pab2 modulates intron-dependent regulation of gene expression in C. neoformans. PAB2 deletion partially restored accumulation of intronless mRNA. In addition, our results demonstrated that the essential nucleases Rrp44p and Xrn2p are implicated in the degradation of mRNA transcribed from an intronless allele in C. neoformans. Double mutant constructions and over-expression experiments suggested that Pab2p and Xrn2p could act in the same pathway whereas Rrp44p appears to act independently. Finally, deletion of the RRP6 or the CID14 gene, encoding the nuclear exosome nuclease and the TRAMP complex associated poly(A) polymerase, respectively, has no effect on intronless allele expression.
大多数新型隐球菌基因都被内含子打断，并且经常发生选择性剪接。在这项研究中，我们研究了内含子对新型隐球菌基因表达的影响。对于大多数测试的基因，消除内含子会大大降低 mRNA 的积累。引人注目的是，内含子的数量和位置以累积的方式调节基因表达水平。筛选能够功能性表达无内含子等位基因的突变株表明，核多聚(A)结合蛋白 Pab2 调节新型隐球菌中内含子依赖的基因表达调控。PAB2 缺失部分恢复了无内含子 mRNA 的积累。此外，我们的结果表明，必需核酶 Rrp44p 和 Xrn2p 参与了新型隐球菌中无内含子等位基因转录的 mRNA 的降解。双突变体构建和过表达实验表明，Pab2p 和 Xrn2p 可能在同一途径中发挥作用，而 Rrp44p 似乎独立发挥作用。最后，缺失编码核 exosome 核酸酶和与 TRAMP 复合物相关的 poly(A) 聚合酶的 RRP6 或 CID14 基因对无内含子等位基因的表达没有影响。
