Search

The Drosophila RNA-binding protein Sex-lethal (Sxl) is a potent post-transcriptional regulator of gene expression that controls female development. It regulates the expression of key factors involved in sex-specific differences in morphology, behavior, and dosage compensation. Functional Sxl protein is only expressed in female flies, where it binds to U-rich RNA motifs present in its target mRNAs to regulate their fate. Sxl is a very versatile regulator that, by shuttling between the nucleus and the cytoplasm, can regulate almost all aspects of post-transcriptional gene expression including RNA processing, nuclear export, and translation. For these functions, Sxl employs multiple interactions to either antagonize RNA-processing factors or to recruit various coregulators, thus allowing it to establish a female-specific gene expression pattern. Here, we summarize the current knowledge about Sxl function and review recent mechanistic and structural studies that further our understanding of how such a seemingly 'simple' RNA-binding protein can exert this plethora of different functions., (© 2017 The Authors. FEBS Letters published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

Many viral mRNAs contain a 5'-UTR RNA element called internal ribosome-entry site (IRES), which bypasses the requirement of some canonical initiation factors allowing cap-independent translation. The IRES of hepatitis-C virus drives translation by directly recruiting 40S ribosomal subunits and binds to eIF3 which plays a critical role in both cap-dependent and cap-independent translation. However, the molecular basis for eIF3 activity in either case remains enigmatic. Here we report that subunit b of the eIF3 complex directly binds to HCV IRES domain III via its N-terminal-RRM. Because eIF3b was previously shown to be involved in eIF3j binding, biological implications are discussed.