We are studying the hematopoietic transcription factor and oncoprotein c-Myb. This factor regulates many genes during blood cell development, from stem cells to more mature cells. It also promotes specific forms of human cancers such as leukaemia, breast cancer, and colorectal cancers when deregulated. If c-Myb is lost, no blood is formed, and when c-Myb is altered, normal growth control is disturbed. Our aim is to understand the underlying mechanisms of c-Myb function. We recently discovered that c-Myb operates as a “pioneer factor”, with a particular ability to penetrate and open chromatin, an important property during development when gene programs have to be modulated [Fuglerud et al. 2017].
Posttranslational modifications (PTMs), such as phosphorylations, are widely explored mechanisms of controlling protein functions. Modification of proteins with small ubiquitin-related modifiers (SUMOs) has recently been established as one of the key regulatory modifications in eukaryotic cells, significantly affecting fundamental nuclear processes such as transcription and chromatin organization. A large number of transcription factors and cofactors are SUMO-modified, which in most cases are associated with repression. Research in our lab has revealed that SUMO-conjugation and –binding are important regulatory mechanisms for c-Myb function [Molværsmyr et al. 2010; Sæther et al. 2011; Ledsaak et al. 2016]. Furthermore, c-Myb may change the epigenetic state of chromatin and influence histone tail modifications [Molværsmyr et al. 2010]. One implication of this potent repressive mechanism is that relief of SUMO-mediated repression may represent a significant contribution to gene activation. This derepression is still poorly understood and is the subject of ongoing research in Gabrielsens lab (the MARS project), where we aim to unravel novel mechanisms of gene activation based on the controlled relief of SUMO-mediated repression of transcription. Also in these studies, we use the transcription factor c-Myb as model.
In our research we apply a broad range of methods. Working in the Gabrielsen lab will therefore provide the student with a very useful repertoire of techniques. Methods involved: plasmid design, PCR and subcloning, gene knock-down, transfection of mammalian cell cultures, reporter assays, western blots, GST-pulldown assays, co-immunoprecipitations, imaging. RNA-seq, ChIP-seq, ATAC-seq have recently been added to our repertoire.
We invite 1-2 enthusiastic master students to participate in these studies.
Project 1: Analysis of gene networks regulated by c-Myb
We have recently obtained several global datasets that contain important information on genes regulated by c-Myb and genomic regulatory sites where c-Myb operates (RNA-seq, ATAC-seq, ChIP-seq). We invite a master student to participate in the analysis and follow-up of these gold mines of information.
Project 2: Examining PTM mechanisms for derepression
The role of SUMO-PTMs in the relief of repressive effects of SUMOylation is only beginning to emerge. We will address whether a recently described SUMO acetylation switch applies to c-Myb, try to identify the acetyl transferase involved and to dissect the underlying mechanism. Based on our functional studies of HIPK1 in relation to c-Myb and SUMO status, we hypothesize that such kinases may also be part of a derepression mechanism based on PTMs. Therefore we will investigate HIPK-mediated phosphorylation of p300 and of SUMO itself as possible derepression mechanisms contributing to relief of SUMO-mediated repression.