ABSTRACT
The gene vestigial (vg) plays a key role in indirect flight muscle (IFM) development. We show here that vg is controlled by the Notch anti-myogenic signaling pathway in myoblasts and is regulated by a novel 822 bp enhancer during IFM differentiation. Interestingly, this muscle enhancer is activated in developing fibers and in a small number of myoblasts before the fusion of myoblasts with the developing muscle fibers. Moreover, we show that this enhancer is activated by Drosophila Myocyte enhancing factor 2 (MEF2), Scalloped (SD) and VG but repressed by Twist, demonstrating a sensitivity to differentiation in vivo. In vitro experiments reveal that SD can directly bind this enhancer and MEF2 can physically interact with both SD and TWI. Cumulatively, our data reveal the interplay between different myogenic factors responsible for the expression of an enhancer activated during muscle differentiation.
Subject(s)
Cell Differentiation/physiology , Drosophila Proteins/genetics , Drosophila melanogaster , Enhancer Elements, Genetic , Gene Expression Regulation, Developmental , Nuclear Proteins/genetics , Signal Transduction/physiology , Animals , Cell Line , Drosophila Proteins/metabolism , Drosophila melanogaster/anatomy & histology , Drosophila melanogaster/embryology , Drosophila melanogaster/genetics , Flight, Animal , Muscles/embryology , Muscles/physiology , Myoblasts/cytology , Myoblasts/physiology , Myogenic Regulatory Factors/genetics , Myogenic Regulatory Factors/metabolism , Nuclear Proteins/metabolism , Receptors, Notch/genetics , Receptors, Notch/metabolism , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Transcription Factors/genetics , Transcription Factors/metabolism , Twist-Related Protein 1/genetics , Twist-Related Protein 1/metabolismABSTRACT
The genomic stability of the rDNA tandem array is tightly controlled to allow sequence homogenization and to prevent deleterious rearrangements. In this report, we show that the absence of the yeast CTD kinase I (CTDK-I) complex in null mutant strains leads to a decrease in the number of tandem rDNA repeats. Reintroduction of the missing gene induces an increase of rDNA repeats to reach a copy number similar to that of the original strain. Interestingly, while expansion is dependent on Fob1, a protein required for replication fork blocking activity in rDNA, contraction occurs in the absence of Fob1. Furthermore, silencing of class II genes at the rDNA, a process connected to rDNA stability, is not affected. Ctk1, the kinase subunit of the CTDK-I complex is involved in various steps of mRNA synthesis. In addition, we have recently shown that Ctk1 is also implicated in rRNA synthesis. The results suggest that the RNA polymerase I transcription defect occurring in a ctk1 mutant strain causes rDNA contraction.
Subject(s)
DNA, Ribosomal/genetics , Genes, rRNA , Protein Kinases/physiology , Saccharomyces cerevisiae Proteins/physiology , Saccharomyces cerevisiae/enzymology , Saccharomyces cerevisiae/genetics , Cell Cycle Proteins/metabolism , Chromosomal Proteins, Non-Histone/metabolism , DNA, Ribosomal/analysis , DNA-Binding Proteins/physiology , Gene Deletion , Gene Silencing , Multigene Family , Nuclear Proteins/metabolism , Protein Kinases/genetics , RNA Polymerase I/metabolism , Saccharomyces cerevisiae Proteins/genetics , Transcription, Genetic , CohesinsABSTRACT
RNA polymerase II carboxy terminal domain (CTD) kinases are key elements in the control of mRNA synthesis. Yeast CTD kinase I (CTDK-I), is a non-essential complex involved in the regulation of mRNA synthesis at the level of transcription elongation, pre-mRNA 3' formation and nuclear export. Here, we report that CTDK-I is also involved in ribosomal RNA synthesis. We show that CTDK-I is localized in part in the nucleolus. In its absence, nucleolar structure and RNA polymerase I transcription are affected. In vitro experiments show an impairment of the Pol I transcription machinery. Remarkably, RNA polymerase I co-precipitates from cellular extracts with Ctk1, the kinase subunit of the CTDK-I complex. In vitro analysis further demonstrates a direct interaction between RNA polymerase I and Ctk1. The results suggest that CTDK-I might participate in the regulation of distinct nuclear transcriptional machineries, thus playing a role in the adaptation of the global transcriptional response to growth signalling.