Nucleolin Interacts and Co-Localizes with Components of Pre-Catalytic Spliceosome Complexes

Abstract

Nucleolin is an RNA binding protein that is involved in many post-transcriptional regulation steps of messenger RNAs in addition to its nucleolar role in ribosomal RNA transcription and assembly in pre-ribosomes. Acetylated nucleolin was found to be associated with nuclear speckles and to co-localize with the splicing factor SC35. Previous nuclear pull down of nucleolin identified several splicing components and factors involved in RNA polymerase II transcription associated with nucleolin. In this report, we show that these splicing components are specifics of the pre-catalytic A and B spliceosomes, while proteins recruited in the Bact, C and P complexes are absent from the nucleolin interacting proteins. Furthermore, we show that acetylated nucleolin co-localized with P-SF3B1, a marker of co-transcriptional active spliceosomes. P-SF3B1 complexes can be pulled down with nucleolin specific antibodies. Interestingly, the alternative splicing of Fibronectin at the IIICS and EDB sites was affected by nucleolin depletion. These data are consistent with a model where nucleolin could be a factor bridging RNA polymerase II transcription and assembly of pre-catalytic spliceosome similarly to its function in the co-transcriptional maturation of pre-rRNA.

Retracted: Alternative splicing modulation mediated by G-quadruplex structures in MALAT1 lncRNA

“…Therefore, its function is highly implicated in AS. NCL in the nuclear speckles colocalizes with SC35 (as we also observe in our study), and is reported to interact with the pre-catalytic spliceosome complex and regulate AS of fibronectin ( 80 ). NCL is also known to play a major role in splice site selection ( 81 ).…”

A Novel Role for Nucleolin in Splice Site Selection

“…Recent studies have indicated a connection of NCL with splicing factors (44)(45)(46)(47). We have previously found NCL as an integral component of the endogenous spliceosome (supraspliceosome), where it was identified associated with specific supraspliceosomes at all splicing stages (33).…”

Nucleolin: a prognostic marker in cancer?

“…It has been suggested that the transient interaction of nucleolin with the pre-rRNA during transcription might be involved in the correct folding of the long pre-RNA which is required for the processing in mature ribosomal RNA [13][14][15][16][17] but it remains to be demonstrated if the RNA binding specificity of nucleolin towards pre-rRNA is important as deletion of the RNA binding domains responsible for this specificity do not seems to be crucial for the vital function of nucleolin [7]. By analogy to this co-transcriptional role of nucleolin in pre-rRNA maturation and assembly with proteins, it has been recently suggested that acetylated nucleolin could also be involved in the assembly of pre-catalytic spliceosomes and in splicing reaction [18,19]. Several reports suggest also that nucleolin could be involved in the regulation of transcription of some ANP polymerase II genes [20][21][22][23][24].…”