Arabidopsis Decapping 5 Is Required for mRNA Decapping, P-Body Formation, and Translational Repression during Postembryonic Development

Abstract

Eukaryotic processing bodies (P-bodies) are implicated in mRNA storage and mRNA decapping. We previously found that a decapping complex comprising Decapping 1 (DCP1), DCP2, and Varicose in Arabidopsis thaliana is essential for postembryonic development, but the underlying mechanism is poorly understood. Here, we characterized Arabidopsis DCP5, a homolog of human RNA-associated protein 55, as an additional P-body constituent. DCP5 associates with DCP1 and DCP2 and is required for mRNA decapping in vivo. In spite of its association with DCP2, DCP5 has no effect on DCP2 decapping activity in vitro, suggesting that the effect on decapping in vivo is indirect. In knockdown mutant dcp5-1, not only is mRNA decapping compromised, but the size of P-bodies is also significantly decreased. These results indicate that DCP5 is required for P-body formation, which likely facilitates efficient decapping. During wild-type seed germination, mRNAs encoding seed storage proteins (SSPs) are translationally repressed and degraded. By contrast, in dcp5-1, SSP mRNAs are translated, leading to accumulation of their products in germinated seedlings. In vitro experiments using wheat germ extracts confirmed that DCP5 is a translational repressor. Our results showed that DCP5 is required for translational repression and P-body formation and plays an indirect role in mRNA decapping.

Posttranscriptional Control of Photosynthetic mRNA Decay under Stress Conditions Requires 3′ and 5′ Untranslated Regions and Correlates with Differential Polysome Association in Rice

“…1C). Cordycepin treatments were effective in rice in blocking transcription, as evidenced by the reduced half-lives of EXPL2 (AK068088) and SEN1 (AK120910), rice homologs of Arabidopsis genes that produce very unstable mRNAs (Gutierrez et al, 2002;Lidder et al, 2005;Xu and Chua, 2009), under normal growth conditions (Supplemental Fig. S5).…”

The role of decapping proteins in the miRNA accumulation inArabidopsis thaliana

“…DCP5 is a component of the decapping complex, but it does not promote the decapping activity, whereas DCP1 and VCS do. 45 The distinct functions in decapping of DCP1, DCP2 and VCS, independent from DCP5, may cause the decrease in miRNA levels in dcp1, dcp2 and vcs mutants. However, because dcp5-1 is a knockdown mutant, we need to determine if the miRNA accumulation decreases in the dcp5 knockout mutant.…”

“…1,2 It was previously reported that DCP5 interacts with DCP1, DCP2 and VCS in the P-body, and plays a role in the decapping in vivo. 45 To confirm whether this decapping co-activator is involved in miRNAs and siRNA accumulation, we examined the accumulation of miRNAs and siRNA in dcp5-1, a dcp5-impaired mutant. Unlike in dcp1-1, dcp2-1 and vcs-6 (Fig.…”

RGG motif proteins: Modulators of mRNA functional states

“…First, scd6Δ strains show a synthetic defect in decapping with the edc3Δ 44 (Edc3 is another related activator of decapping). 43 Second, Scd6, Dcp5 (Arabidopsis ortholog of Scd6) and the S. pombe Scd6 physically interact with purified Dcp2 but do not stimulate its decapping activity, 45,46 A final implication of this work and one from other labs is that eIF4G could be an integrator of functional states of mRNA. eIF4G can provide a scaffold to recruit proteins that negatively affect translation, such as RGG motif proteins, 1 Khd1 20 and L13a.…”