Iws1 and Spt6 Regulate Trimethylation of Histone H3 on Lysine 36 through Akt Signaling and are Essential for Mouse Embryonic Genome Activation

Abstract

The mRNA processing and export factor, Iws1, interacts with the histone H3/H4 chaperone, Spt6 (Supt6 in mouse gene ontology) and recruits the lysine methyltransferase, Setd2, to chromatin to regulate H3K36me3. This recruitment is known to be crucial for pre-mRNA splicing and Iws1 has been shown to interact with REF1/Aly to mediate mRNA export. However, the role of this complex has not yet been examined in embryonic development. Here, we show that knockdown of either Iws1 or Supt6 blocked embryo development, primarily at the 8/16-cell stage, indicating that Iws1 and Supt6 are crucial for mouse preimplantation development. In the knockdown embryos, we observed decreases in pre-mRNA splicing, mRNA export and the expression of the lineage-specific transcription factor, Nanog. We found that either Iws1 or Supt6 are required for H3K36 trimethylation and that concurrent knockdown of both Iws1 and Supt6 blocks embryonic development at the 2-cell stage. We show that H3K36me3 is modulated by the Pi3k/Akt pathway, as inhibition of this pathway reduced the global level of H3K36me3 while activation of the pathway increased the level of this modification in 2-cell embryos. We observed that Iws1 interacts with nuclear Akt in early embryos, and herein propose that Akt modulates H3K36me3 through interaction with Iws1. Together, our results indicate that the Iws1 and Supt6 play crucial roles in embryonic genome activation, lineage specification, and histone modification during mouse early development.

The conserved elongation factor Spn1 is required for normal transcription, histone modifications, and splicing in Saccharomyces cerevisiae

“…Given previous studies that suggested a role for Spn1 in H3K36 methylation ( 3 , 5 , 14 ) and the change we observed in Set2 recruitment after Spn1 depletion (Figure 4E - G ), we used ChIP-seq to measure the genome-wide occupancy of H3K36me2 and H3K36me3 in Spn1-depleted and non-depleted conditions. In these experiments, we also included analysis of H3K4 trimethylation (H3K4me3), given the genetic relationship between Spn1 and the enzymes required for the methylation and demethylation of H3K4 ( 21 , 22 ).…”

“…Since both Spn1 and H3K36 methylation have been previously implicated in splicing ( 3 , 5 , 85–89 ), we looked for changes in splicing efficiency after Spn1 depletion by using our RNA-seq data to estimate intron retention (see Materials and Methods). We observed a general tendency for increased intron retention after Spn1 depletion (Figure 7A ), particularly in ribosomal protein transcripts, whose high expression levels gave us greater power to detect changes in intron retention.…”

“…Spn1 was first identified in S. cerevisiae as a protein that interacts physically and genetically with factors involved in transcription ( 1 , 7–9 ), and it was later found to be part of the general RNA polymerase II (RNAPII) elongation complex on actively transcribed genes ( 10 ). Several studies have suggested that Spn1 is involved in transcription and co-transcriptional processes, including transcriptional activation ( 1 , 11 , 12 ), elongation ( 1 , 8–10 ), pre-mRNA processing ( 3 , 5 , 13–15 ), and mRNA nuclear export ( 3 , 13 , 14 ). The recent demonstration that Spn1 binds histones and assembles nucleosomes in vitro suggested that Spn1 functions as a histone chaperone ( 16 ).…”

The elongation factor Elof1 is required for mammalian gastrulation

“…Components of the RNApII elongation complex interact with histones and this complex also plays important roles in pre-mRNA splicing (reviewed in [19]). The yeast orthologue of Elof1, Elf1, interacts with Iws1 (Spt1) to facilitate histone H3K36 trimethylation (H3K36me3) modification, and recent studies show that Iws1 is also essential for early murine development [20, 21]. In higher eukaryotes H3K36me3 is linked to alternative splicing through the recruitment of polypyrimidine tract-binding protein (PTB) [22, 23].…”

Transcriptome analysis of in vitro fertilization and parthenogenesis activation during early embryonic development in pigs

“…splicing-related genes, such as SRSF7, HNRNPA2B1, and IWS1(Despic et al, 2017;Kasowitz et al, 2018;Oqani et al, 2019), had vital effects on early embryonic development. Moreover, some biological process related to embryonic development have occurred in advance from morula to early blastocyst in PA, such as positive regulation of kidney development, retina development in cameratype eye, and inner ear receptor cell differentiation.…”