DcpS scavenger decapping enzyme can modulate pre-mRNA splicing

Abstract

The human scavenger decapping enzyme, DcpS, functions to hydrolyze the resulting cap structure following cytoplasmic mRNA decay yet is, surprisingly, a nuclear protein by immunofluorescence. Here, we show that DcpS is a nucleocytoplasmic shuttling protein that contains separable nuclear import and Crm-1-dependent export signals. We postulated that the presence of DcpS in both cellular compartments and its ability to hydrolyze cap structure may impact other cellular events dependent on capbinding proteins. An shRNA-engineered cell line with markedly diminished DcpS levels led to a corresponding reduction in capproximal intron splicing of a reporter minigene and endogenous genes. The impaired cap catabolism and resultant imbalanced cap concentrations were postulated to sequester the cap-binding complex (CBC) from its normal splicing function. In support of this explanation, DcpS efficiently displaced the nuclear cap-binding protein Cbp20 from cap structure, and complementation with Cbp20 reversed the reduced splicing, indicating that modulation of splicing by DcpS is mediated through Cbp20. Our studies demonstrate that the significance of DcpS extends beyond its well-characterized role in mRNA decay and involves a broader range of functions in RNA processing including nuclear pre-mRNA splicing.

DcpS is a transcript-specific modulator of RNA in mammalian cells

“…2A; Shen et al 2008). Consistent with the outcome of RG3039 treated cells, steady-state levels of both HS370762 RNA levels are presented relative to actin mRNA and derived from at least three independent experiments.…”

“…The requirement of DcpS decapping activity and the lack of detectable interaction between DcpS and Xrn1 suggest a potential indirect mechanism. Whether accumulation of cap structure, as implicated in the efficiency of first intron splicing (Bail and Kiledjian 2008;Shen et al 2008) or possible cap structure byproducts generated in the absence of DcpS (Taverniti and Séraphin 2014) may influence Xrn1 activity remains to be determined.…”

“…Affinity-purified DcpS polyclonal antibody (1:200 dilution) (Shen et al 2008) and monoclonal anti-GAPDH antibody (1:1000 dilution, Santa Cruz) were used for Western blot analysis and visualized using secondary antibodies coupled to horseradish peroxidase (Jackson ImmunoResearch) and chemiluminescence (ECL; GE Healthcare).…”

Newborn screening for spinal muscular atrophy: Anticipating an imminent need

“…The role of DcpS is best understood in the degradation of the 5 0 cap during the 3 0 to 5 0 mRNA decay; it may have additional functions in nuclear-cytoplasm transportation and first intron pre-mRNA splicing. 76 Quinazoline is anticipated to progress to Phase I clinical trials (Table 1)…”

Affinity resins containing enzymatically resistant mRNA cap analogs—a new tool for the analysis of cap-binding proteins

“…As a key regulator of the free cap structure, and consequently of the pool of available cap-binding proteins, DcpS is considered an important general modulator of capdependent processes (Bail and Kiledjian 2008). For example, mammalian DcpS is important for efficient removal of the cap-proximal intron, a process depending on CBCmediated association of U1 snRNP to the 59 splice site (Shen et al 2008). DcpS depletion entails reduced first intron removal by sequestering CBC from the cap structure as a result of an imbalanced cap level.…”