Biology Reference
In-Depth Information
Fig. 4
Conservation of HCMV miRNAs in chimpanzee cytomegalovirus (CCMV). Alignment
and secondary structure of two HCMV pre-miRNAs predicted to be conserved in CCMV. HCMV
miRNA sequences found in the miRNA registry were aligned with the publicly available CCMV
genome sequence (Davison et al. 2003). Sequences for HCMV pre-miRNAs and predicted CCMV
pre-miRNAs are shown in (i), secondary structures are compared in (ii), finally alignment of
sequences flanking the respective premiRNAs are compared in (iii). Mismatched bases are
highlighted
et al. 2005; Cui et al. 2006). However, neither of these conserved miRNAs has been
demonstrated to be expressed by either virus. Finally, Marek's disease viruses one and
two (MDV-1, -2), closely related avian alpha herpesviruses, have been shown to
express miRNAs (Burnside et al. 2006; Yao et al. 2007). Interestingly, while these
miRNAs are conserved in their genomic location, none of the miRNAs possess
sequence homology (Yao et al. 2007). It will be interesting to reevaluate the relatedness
of viral miRNAs in terms of their function, as more targets of these miRNAs are
identified.
Genomic Arrangement of HCMV miRNAs
As mentioned above, one of the distinguishing features of HCMV miRNAs is that
they are widely distributed across the genome (Fig. 3). In contrast, miRNAs identified
in all other herpes viruses to date are clustered in short regions of the genome, usually
less than 5 kbp. An additional important difference is that all herpesvirus-encoded
miRNAs are encoded in regions of the genome that are transcriptionally active during
latency. Due to the lack of a simple tissue culture model for HCMV latency, transcrip-
tionally active regions of the viral genome during latency remain controversial.
