Regulatory role of CsuR (YiaU) in determination of cell surface properties of Escherichia coli K-12.

Genomic SELEX screening was performed to identify the binding sites of YiaU, an uncharacterized LysR family transcription factor, on the Escherichia coli K-12 genome. Five high-affinity binding targets of YiaU were identified, all of which were involved in the structures of the bacterial cell surface such as outer and inner membrane proteins, and lipopolysaccharides. Detailed in vitro and in vivo analyses suggest that YiaU activates these target genes. To gain insight into the effects of YiaU in vivo on physiological properties, we used phenotype microarrays, biofilm screening assays and the sensitivity against serum complement analysed using a yiaU deletion mutant or YiaU expression strain. Together, these results suggest that the YiaU regulon confers resistance to some antibiotics, and increases biofilm formation and complement sensitivity. We propose renaming YiaU as CsuR (regulator of cell surface).

Phosphorylation of the RSRSP stretch is critical for splicing regulation by RNA-Binding Motif Protein 20 (RBM20) through nuclear localization.

RBM20 is a major regulator of heart-specific alternative pre-mRNA splicing of TTN encoding a giant sarcomeric protein titin. Mutation in RBM20 is linked to autosomal-dominant familial dilated cardiomyopathy (DCM), yet most of the RBM20 missense mutations in familial and sporadic cases were mapped to an RSRSP stretch in an arginine/serine-rich region of which function remains unknown. In the present study, we identified an R634W missense mutation within the stretch and a G1031X nonsense mutation in cohorts of DCM patients. We demonstrate that the two serine residues in the RSRSP stretch are constitutively phosphorylated and mutations in the stretch disturb nuclear localization of RBM20. Rbm20 S637A knock-in mouse mimicking an S635A mutation reported in a familial case showed a remarkable effect on titin isoform expression like in a patient carrying the mutation. These results revealed the function of the RSRSP stretch as a critical part of a nuclear localization signal and offer the Rbm20 S637A mouse as a good model for in vivo study.