microRNAs stimulate translation initiation mediated by HCV-like IRESes.

MicroRNAs (miRNAs) are small non-coding RNAs that control gene expression by recognizing and hybridizing to a specific sequence generally located in the 3΄ untranslated region (UTR) of targeted mRNAs. miRNA-induced inhibition of translation occurs during the initiation step, most probably at the level of ribosome scanning. In this process, the RNA-induced silencing complex interacts both with PABP and the 43S pre-initiation complex to disrupt scanning of the 40S ribosome.

Translation initiation of the HIV-1 mRNA.

Translation initiation of the full-length mRNA of the human immunodeficiency virus can occur via several different mechanisms to maintain production of viral structural proteins throughout the replication cycle. HIV-1 viral protein synthesis can occur by the use of both a cap-dependant and IRES-driven mechanism depending on the physiological conditions of the cell and the status of the ongoing infection. For both of these mechanisms there is a need for several viral and cellular co-factors for optimal translation of the viral mRNA.