ИСТИНА

Echoviruses and coxsackieviruses are positive-strand RNA viruses causing various human diseases [1]. Like other Picornaviridae, they use internal ribosome entry sites (IRESs) to direct translation of their mRNAs [2]. However, the molecular mechanisms underlying the synthesis of their proteins are poorly understood. To find human genes involved in the echovirus life cycle, we performed CRISPR/Cas knockout screen for the resistance of cultured HEK293T cells to cytopathic infection caused by Echo6, Echo11, Echo19, and Echo30 viruses. We identified MBNL1 (Muscleblind Like Splicing Regulator 1), a gene encoding an RNA-binding protein involved in alternative mRNA splicing, as necessary for the infection. The MBNL1 protein is a partner of another splicing regulator, PTBP1 [3], which is well known as the IRES trans-acting factor (ITAF) required for the activity of a number of picornavirus IRESs [2]. We hypothesized that MBNL1 is also an ITAF involved in the IRES-mediated translation. A monoclonal MBNL1 knockout (KO) cell line was prepared and infected with various enteroviruses. Echoviruses Echo6, Echo7, Echo14, Echo19, and Echo30, as well as coxsackie A viruses CVA7 and CVA16 showed a 3-4 day-long delay in the induction of MBNL1 KO cell death, as compared to the wild-type HEK293T cells, while CVA9 had no cytopathic effect on the KO cells at all. In contrast, coxsackie B viruses CVB3, CVB4, and CVB5, as well as polioviruses PV1, PV2, and PV3 did not require MBNL1. The importance of MBNL1 for the enterovirus IRES-mediated translation was investigated with reporter constructs in mRNA-transfected cells and in a cell-free system. Its role in the virus life cycle will be discussed. The study was supported by the Russian Science Foundation (grant no. 20-14-00178). ------------ References ----------- [1] Lee et al. (2010) J. Clin. Virol. 49, 175-179. [2] Sorokin et al. (2021) Biochemistry (Moscow) 86, 1060–1094. [3] Gooding et al. (2013) Nucleic Acids Res. 41, 4765–4782.