SRrp37, a novel splicing regulator located in the nuclear speckles and nucleoli, interacts with SC35 and modulates alternative pre‐mRNA splicing in vivo

Abstract

We report here the identification and characterization of a novel SR-related protein, referred to as SRrp37, based on its apparent molecular weight and subcellular location. SRrp37 was identified through a yeast two-hybrid screen during the course of searching for proteins interacting with pNO40, a ribosomal 60S core subunit. SRrp37 exhibited two alternative spliced isoforms generated by differential usage of the translation start site with the longer one, SRrp37, initiating at first exon and the shorter, SRrp37-2, starting from exon 2. Three distinct motifs can be discerned in the SRrp37 protein: (1) a serine-arginine (SR) dipeptide enriched domain, (2) a polyserine stretch, and (3) a potential nucleolar localization signal comprising a long array of basic amino acids. SRrp37's message was translated in tissue-specific patterns with both isoforms expressed at comparable levels in tissues showing expression. Indirect immunofluorescence analysis with an anti-SRrp37 antibody, as well as an experiment using myc-tagged proteins, demonstrated that SRrp37 was localized in nucleoli and nuclear speckles. GST pull-down assay showed that SRrp37 interacted physically with SC35. Using adenovirus E1A and chimeric calcitonin/dhfr constructs as splicing reporter minigenes, we found that SRrp37 modulated alternative 5' and 3' splicing in vivo. Together, SRrp37 may participate directly in splicing regulation or indirectly through interaction with SC35. Studies on this novel splicing regulator may provide new information on the intricate splicing machinery as related to the RNA metabolism involving processing of mRNA and rRNA.

The polyserine domain of the lysyl-5 hydroxylase Jmjd6 mediates subnuclear localization

“…A previous study identified 59 proteins with polyS regions in the human genome; it is proposed that replicative slippage at the DNA level was most likely responsible for their facile evolution [8]. It is unclear if our proposed role for the polyS region of Jmjd6 applies to other polyS-containing proteins; however, SRrp37 possesses a polyS domain and has a dual localization in nuclear speckles and in the nucleolus [12]. This conclusion suggests that the function, and related structure, of the Jmjd6 polyS domain are probably also conserved.…”

ZCCHC17 is a master regulator of synaptic gene expression in Alzheimer’s disease

“…ZCCHC17 is a poorly understood protein that has been shown to interact with transcription factors (Chang et al, 2003;Joo et al, 2010) as well as splicing factors (Lin et al, 2017;Ouyang, 2009). ZCCHC17 contains a zinc-finger (CCHC) domain and a nuclear localization signal, and microscopy has localized ZCCHC17 to the nucleus and nucleolus (Chang et al, 2003;Gueydan et al, 2002;Lin et al, 2017;Ouyang, 2009). Although there is no published experimental study of ZCCHC17 protein in brain tissue, a recent metaanalysis of RNA expression data from six previous gene expression studies of AD brain tissue included ZCCHC17 as one of the top 30 most reliably downregulated genes in AD (Li et al, 2015).…”

The intrinsic disorder alphabet. III. Dual personality of serine

“…155 This protein serves as a splicing regulator located in the nuclear speckles and nucleoli 155 and is predicted to be highly disordered. SRrp37 is involved in modulation of alternative pre-mRNA splicing with either 5' distal site activation or preferential use of 3' proximal site, and in case of infection by Herpes simplex virus (HSVI), this protein may act as a splicing inhibitor of HSVI pre-mRNA.…”

“…SRrp37 is involved in modulation of alternative pre-mRNA splicing with either 5' distal site activation or preferential use of 3' proximal site, and in case of infection by Herpes simplex virus (HSVI), this protein may act as a splicing inhibitor of HSVI pre-mRNA. 155 The characteristic features of SRrp37 are high serine (13.5%) and arginine contents (12.8%) and the presence of 3 motifs, a serine-arginine (SR) dipeptide enriched region , a polyserine stretch (residues 258-282), and a potential nucleolar localization signal comprising a long array of basic amino acids (residues 286-312). 155 Scaffolding protein piccolo Piccolo is a 5065 residue-long scaffold protein, which is predicted to be highly disordered (it contains »85% disordered residues).…”

“…155 The characteristic features of SRrp37 are high serine (13.5%) and arginine contents (12.8%) and the presence of 3 motifs, a serine-arginine (SR) dipeptide enriched region , a polyserine stretch (residues 258-282), and a potential nucleolar localization signal comprising a long array of basic amino acids (residues 286-312). 155 Scaffolding protein piccolo Piccolo is a 5065 residue-long scaffold protein, which is predicted to be highly disordered (it contains »85% disordered residues). High level of disorder is a characteristic feature of scaffold proteins that helps them to organize and maintain stable and dynamic protein complexes.…”