Translational repression of cyclin D3 by a stable G-quadruplex in its 5′ UTR: implications for cell cycle regulation

Abstract

cyclin D3 (CCND3) is one of the three D-type cyclins that regulate the G1/S phase transition of the cell cycle. Expression of CCND3 is observed in nearly all proliferating cells; however, the presence of high levels of CCND3 has been linked to a poor prognosis for several types of cancer. Therefore, further mechanistic studies on the regulation of CCND3 expression are urgently needed to provide therapeutic implications. In this study, we report that a conserved RNA G-quadruplex-forming sequence (hereafter CRQ), located in the 5' UTR of mammalian CCND3 mRNA, is able to fold into an extremely stable, intramolecular, parallel G-quadruplex in vitro. The CRQ G-quadruplex dramatically reduces the activity of a reporter gene in human cell lines, but it has little impact on its mRNA level, indicating a translational repression. Moreover, the CRQ sequence in its natural context inhibits translation of CCND3. Disruption of the G-quadruplex structure by G/U-mutation or deletion results in an elevated expression of CCND3 and an increased phosphorylation of Rb, a downstream target of CCND3, which promotes progression of cells through the G1 phase. Our results add to the growing understanding of the regulation of CCND3 expression and provide a potential therapeutic target for cancer treatment.

SASH1, a new potential link between smoking and atherosclerosis

“…Accordingly, SASH1 silencing resulted in an increased CCND1 protein expression, as previously shown in A549 cells 11 , as well as the increased CCND3 mRNA and protein levels. Both cyclins are part of the cyclin-dependent kinase protein complex required for the G 1 /S transition 161,162 and are known to be co-expressed 163 . However, as SASH1 over-expressing cells have been shown to be arrested in the G 1 phase 137 , it is likely that the increase of CCND1 and CCND3 expression reflects an indirect effect due to SASH1 silencing thus favoring the G 1 /S transition rather than a direct effect of SASH1 increasing their expression.…”

A stable RNA G-quadruplex within the 5′-UTR of Arabidopsis thaliana ATR mRNA inhibits translation

“…To investigate the effect of flanking sequence on the RNA secondary structure, we used ILP [70] on the competing GUrich hairpin (nt 1-37) (Supplementary Figure S3A), the hairpinquadruplex (nt 1-42) (Supplementary Figure S3B) [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41]. The most obvious difference between ILP of the ATR 5 -UTR in 100 mM K + and 100 mM Li + conditions was in the three loop regions (see 'L1', 'L2' and 'L3' on the right-hand side of Figure 4A) of the GQS, as revealed by the K + /Li + ratio [7] of individual nucleotides ( Figure 4B).…”

“…For example, DNA GQSs have been shown to regulate replication, telomere length and transcription, whereas RNA GQSs in UTRs or ORFs are known to control transcription, translation, frameshifting events, splicing, alternative polyadenylation and localization in mammalian systems [2,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. For example, DNA GQSs have been shown to regulate replication, telomere length and transcription, whereas RNA GQSs in UTRs or ORFs are known to control transcription, translation, frameshifting events, splicing, alternative polyadenylation and localization in mammalian systems [2,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37].…”

Grsf1-Induced Translation of the SNARE Protein Use1 Is Required for Expansion of the Erythroid Compartment

“…Interestingly, also transcripts for TGFβ2 and CyclinD3 contain G-quadruplex structure [1], [56]. TGFβ2 is a Epo-induced gene upregulated during erythroid differentiation [32].…”