Ubiquitination of mRNA cycling sequence binding protein from Leishmania donovani (LdCSBP) modulates the RNA endonuclease activity of its Smr domain

Abstract

Edited by Michael IbbaKeywords: CCCH Zn-finger mRNA turnover Smr domain RNA endonuclease Ubiquitination Leishmania donovani a b s t r a c tIn trypanosomatid parasites, an octanucleotide sequence (C/A)AUAGAA(G/A) in the UTRs primarily determines the stability of S-phase specific mRNAs. A multi-domain protein LdCSBP from Leishmania donovani interacts with the UTR of an S-phase RNA containing the octanucleotide sequence through its unique CCCH-type Zn-finger motifs. Interestingly, the RNA binding protein contains a previously characterized DNA endonuclease domain -Smr. It has been demonstrated here that the LdCSBP Smr domain independently possesses both DNA and RNA endonuclease activities, but the full-length LdCSBP exhibits only riboendonuclease activity. Moreover, LdCSBP protein has been shown to be ubiquitinated, resulting in the down-regulation of its riboendonuclease activity. In conclusion, the results described here suggest a novel regulatory mechanism of mRNA degradation through ubiquitination in eukaryotes.

PPR-SMR protein SOT1 has RNA endonuclease activity

“…2 B and C), which is consistent with the DNA endonuclease activity observed in other SMR-containing proteins (20)(21)(22)(23)(24)(25)(26). In addition, our results showed that the SMR domain of SOT1 has RNA endonuclease activity (Fig.…”

“…Recent studies demonstrated the SMR domain exhibits DNA nicking nuclease activity in vitro (20)(21)(22)(23)(24)(25). Furthermore, a C-terminal SMR domain in Leishmania donovani S-phase mRNA cycling sequence binding protein (CSBP) has RNA cleavage activity in vitro (26). These findings suggest that the SMR domain has nuclease activity.…”

“…The PPR domain can specifically recognize RNAs in an intrinsic sequence-specific manner (5). Previous studies of SMR-containing proteins in other organisms have provided evidence for endonuclease activity of the SMR domain (20)(21)(22)(23)26). However, the function of the enigmatic SMR domain in PPR-SMR proteins has not yet been comprehensively investigated.…”

“…Because SMR domains typically have DNA nicking activity (20)(21)(22)(23)(24)(25)(26), we investigated whether the SMR domain of SOT1 retained the ability to nick supercoiled DNA. We found that recombinant SMR protein SOT1 SMR (amino acids 603-710 of SOT1) cleaved supercoiled pUC19 to open circular and linear conformations and that the metal ions Mn 2+ and Mg 2+ increased the DNA endonuclease activity of SOT1 SMR ( Fig.…”

Post-Transcriptional Regulation by Poly(ADP-ribosyl)ation of the RNA-Binding Proteins

“…RBPs can be modified at the post-translational level by phosphorylation [6–9], ubiquitination [10,11] and poly(ADP-ribosyl)ation (PARylation) [12] to achieve temporal/spatial-specific post-transcriptional control of gene expression. PARylation is performed by Poly(ADP-ribose) polymerases (PARPs), which utilize NAD to synthesize poly(ADP-ribose) polymer (pADPr) with the resulting sizes varying from 2 to 200 ADP-ribose units [13,14] (Figure 1).…”