TFIIH localization is highly dynamic during zygotic genome activation in Drosophila, and its depletion causes catastrophic mitosis

Abstract

In , zygotic genome activation occurs in pre-blastoderm embryos during rapid mitotic divisions. How the transcription machinery is coordinated to achieve this goal in a very brief time span is still poorly understood. Transcription factor II H (TFIIH) is fundamental for transcription initiation by RNA polymerase II (RNAPII). Herein, we show the dynamics of TFIIH at the onset of transcription in embryos. TFIIH shows an oscillatory behaviour between the nucleus and cytoplasm. TFIIH foci are observed from interphase to metaphase, and colocalize with those for RNAPII phosphorylated at serine 5 (RNAPIIS5P) at prophase, suggesting that transcription occurs during the first mitotic phases. Furthermore, embryos with defects in subunits of either the CAK or the core subcomplexes of TFIIH show catastrophic mitosis. Although, transcriptome analyses show altered expression of several maternal genes that participate in mitosis, the global level of RNAPIIS5P in TFIIH mutant embryos is similar to that in the wild type, therefore, a direct role for TFIIH in mitosis cannot be ruled out. These results provide important insights regarding the role of a basal transcription machinery component when the zygotic genome is activated.

Disruption of TFIIH activities generates a stress gene expression response and reveals possible new targets against cancer

“…However, we detected that many transcripts were downregulated and many others were upregulated. These results correlate with our data in Drosophila, in which both up- and downregulated transcripts were observed in p8 and p52 mutant organisms [ 37 , 38 ]. Interestingly, the increase in the levels of several specific genes in response to TPL also occurred in other breast cancer cell lines.…”

“…While analysing the transcriptome of TFIIH mutants in Drosophila , we previously reported that not all genes responded equally and that the transcript levels of numerous genes increase in TFIIH mutant tissues [ 37 , 38 ]. Therefore, to explore whether TPL also generates a differential effect on gene expression in TAM and NT cells, we analysed the transcriptomes of these cells after incubation with 125 nM TPL for 4 h, a concentration found to reduce equally RNAPII levels by half in NT and TAM cells, to affect mildly cell viability ( figure 3 a,b ).…”

Nuclear Export of Cyclin B Mediated by the Nup62 Complex Is Required for Meiotic Initiation in Drosophila Males

“…This phosphorylation is one of the essential conditions for the activation of the kinase [23][24][25]47,48]. In Drosophila, the CAK made of Cyclin H and CDK7 is also localized in the nucleus in early embryos [49]. In the Nup62-depleted premeiotic spermatocytes, this phosphorylation occurred, as observed in control cells.…”

Moonlighting in Mitosis: Analysis of the Mitotic Functions of Transcription and Splicing Factors

“…These proteins are enriched around the metaphase chromosomes and in some cases (e.g., p52) they appear to concentrate in a region corresponding to the spindle [113]. Moreover, in embryos from p8 and hay mutant mothers or Cdk7 RNAi mothers, most spindles are morphologically aberrant and show abnormal chromosome segregation [113]. Drosophila Xpd is required for proper spindle dynamics and chromosome segregation in early embryos.…”

“…Studies using fluorescently tagged TFIIH components have shown that Hay, p8, p52, and Cdk7 exhibit similar localization patterns in live early embryos. These proteins are enriched around the metaphase chromosomes and in some cases (e.g., p52) they appear to concentrate in a region corresponding to the spindle [113]. Moreover, in embryos from p8 and hay mutant mothers or Cdk7 RNAi mothers, most spindles are morphologically aberrant and show abnormal chromosome segregation [113].…”