Brian M. Shewchuck, Ph.D.
1991, B.S., The Rochester Institute of Technology (Rochester, NY)

1997, Ph.D., The Pennsylvania State University (University Park, PA )

Research Interests
Molecular mechanisms of eukaryotic gene regulation, particularly in the context of gene clusters. Influence of local chromatin structure and chromosome structural domains on gene expression.
Current Research
Current research involves defining and characterizing the human growth hormone gene cluster locus control region (LCR) with respect to its role in potentiating high levels of somatotrope-specific expression of the human growth hormone gene in transgenic mouse models. The human growth hormone gene cluster is comprised of five genes that are expressed in different tissues in spite of greater that 90% identity in the 5'-flanking and intragenic regions. The GH-N gene encoding growth hormone is expressed exclusively in the somatotropes of the anterior pituitary, whereas the remaining genes encoding the chorionic somatomammotropins (CS-L, CS-A and CS-B) and a variant growth hormone (GH-V) are expressed in the syncytiotrophoblast layer of the placenta. High-level somatotrope-specific expression of hGH-N in transgenic mice requires the activity of part of a distal locus control region (LCR) identified by two closely spaced DNaseI hypersensitive sites (HSs) located ~15 kb upstream of the hGH-N gene (1). Interestingly, this region has essentially no activity in transiently or stably transfected somatotrope and non-somatotrope cell lines. The activity of this region in transgenic mice has been resolved to a ~400 bp fragment (2). The next stage of this work is to identify discrete elements and their cognate transcription factors that interact in this region by in vitro binding assays, and to test the requirement for any identified elements in transgenic mice. The dynamics of the activity of the HSI,II region in pituitary somatotropes during ontogeny, and the mechanistic basis for the exclusivity of the HSI,II activity for the hGH-N gene are also being investigated. The approaches being used in these studies include in vitro gel shifts, footprinting, and site-directed mutagenesis to define cis-trans interactions and such studies are followed by in vivo testing of informative mutations of the LCR elements in transgenic mice using either embryo founder analyses or expression in established lines.
Selected Publications
  1. Shewchuk, B.M., Asa, S.L. Cooke, N.E., and Liebhaber, S.A. 1999. Pit-1 binding sites in the somatotrope-specific HS I,II region of the hGH locus are essential for in vivo LCR-mediated hGH-N gene activation. J. Biol. Chem., 274:35725-35733.

  2. Shewchuk, B. and R. Hardison. 1997. CpG islands from the a-globin gene cluster increase gene expression in an integration-dependent manner. Molecular and Cellular Biology 17:5856-5866.

  3. James-Pederson, M., S. Yost, B. Shewchuk, T. Zeigler, R. Miller and R. Hardison. 1995. Flanking and intragenic sequences regulating the expression of the rabbit a-globin gene. The Journal of Biological Chemistry 270:3965-3973

  4. Yost, S. E., B. Shewchuk and R. Hardison. 1993. Nuclear protein-binding sites in a transcriptional control region of the rabbit a-globin gene. Molecular and Cellular Biology 13:5439-5449
Last Updated: Thu, May 17, 2001