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mdv1-miR-M7-5p, located in the newly identified first intron of the latency-associated transcript of Marek's disease virus, targets the immediate-early genes ICP4 and ICP27
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Edité par HAL CCSD ; Microbiology Society
International audience. Marek's disease virus serotype 1 (MDV-1) is an alphaherpesvirus responsible for T-cell lymphoma in chickens. Its genome organization is similar to that of mardiviruses and simplexviruses: two unique sequences, unique long (UL) and unique short (US), encoding the core genes, are enclosed by the inverted repeat sequences repeat short (RS) and repeat long (RL) (Tulman et al., 2000) (Fig. 1a). As in all other herpesviruses, the life cycle of MDV is divided into a lytic and a latent phase, which is associated with oncogenesis < in MDV (Schat & Nair, 2008). The first genes expressed during herpesvirus lytic infection are the immediate-early (IE) genes, which control viral gene transcription, triggering a cascade of viral gene expression. In MDV, three genes homologous to the IE genes of other alphaherpesviruses have been identified: ICP4 (located in the RS region), ICP22 and ICP27 (UL54). MDV ICP4 and ICP22 have been described as transactivators (Kato et al., 2002; Pratt et al., 1994), whereas MDV ICP27 has been shown to play a role in post-transcriptional gene regulation, by inhibiting both viral and host-cell splicing (Amor et al., 2011), as also reported for other herpesvirus ICP27 homologues (Smith et al., 2005). As in other herpesviruses, the latency of MDV is cha- ; racterized by the overexpression of a limited subset of specific viral genes, including the non-protein-coding latency-associated transcripts (LATs), which are expressed from the RS region and are antisense to the IE gene ICP4 (Baigent & Davison, 2004; Cantello et al., 1994, 1997). The first transcripts of the MDV LAT family to be identified consisted of one large 10 kb unspliced mRNA and two MDV small RNAs (MSRs) corresponding to five exons
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