Erika Mancini – University of Sussex
Matt Guille – University of Portsmouth
Garry Scarlett – University of Portsmouth
During early vertebrate development cell fate is under the control of maternally inherited tissue restricted transcription factors, whose tight regulation is key to prevent abnormal subsequent expression of early genes.
The control of GATA‐2 gene expression by the maternally inherited multisubunit CCAAT box transcription factor (CBTF) is an example of such regulation.
GATA‐2 expression is necessary for both haematopoietic and urogenital development and is implicated in the formation of ventral mesoderm in Xenopus. The CBTF binding site in the GATA‐2 promoter is evolutionarily conserved and is necessary for the correct regulation of its transcription. CBTF is present the oocyte nucleus where gata2 is initially transcribed. However, after oocyte maturation, CBTF activity is cytoplasmic and re-locates to the nucleus only when zygotic gata2 transcription commences. CBTF is anchored in the cytoplasm by RNA binding of one of its subunits, ILF3. The movement of CBTF from the cytoplasm to the nucleus is synchronous with the mass degradation of maternal RNA at the mid-blastula transition suggesting a mechanism for the developmental stage specific control of CBTF activity based on RNA binding.
Surprisingly, despite the importance of such complex little is known about its composition, structure and mechanism of action. The size of the CBTF complex, estimated at 600KDa strongly suggests that it contains more subunits than a single 95KDa ilf3. This project aims to shed light into the molecular mechanism of the CBTF complex by an interdisciplinary approach combining developmental and structural biology. We will (i) explore the composition of the complex and changes that likely occur when transitioning from cytoplasmic to nuclear localization. (ii) unravel sequence specificity when bound to the RNA in the cytoplasm. (iii) determine the structure of the CBTF complex on its own and when bound to the gata2 promoter inverted CCAA T box. This project is of fundamental importance to the understanding of transcription regulation in early embryonic development.