? A tissue-specific locus control region (hGH LCR) regulates the human growth hormone (hGH) gene cluster. The components of the hGH LCR, marked by DNase I hypersensitive sites (HS), are located from 14.5 to 32 kb upstream of the hGH cluster. We have defined HSI, at -14.5 kb, as the major enhancer component of the hGH LCR in pituitary somatotropes. This determinant plays an essential and non-redundant role in hGH-N transgene activation in the mouse pituitary. The hGH LCR and hGH-N gene are encompassed within a continuous 32 kb somatotrope-specific acetylated chromatin domain. HSI contains an array of three binding sites for the pituitary-specific POU-homeodomain trans-factor, Pit-1. These core determinants of HSI are critical for establishment of the broad acetylated domain and for the activation of the hGH-N gene during development. To extend the mechanistic understanding of hGH LCR action we propose the following three aims.
Aim 1. Define cis- and trans-effectors of LCR-mediated long-range transcriptional enhancement.
This aim will focus on the identification of the full complement of cis- and trans-regulatory elements that facilitate HSI-mediated long-range activation of the hGH-N promoter over a distance of 14.5 kb and that define the borders of the modified chromatin domain.
Aim II. Define the mechanism of acetylation spreading within the hGH LCR.
This aim will address the mechanisms by which these determinants establish an extensive domain of chromatin modification and trigger long-range gene activation of the target hGH-N promoter.
Aim III. Establish functional relationships between specific hGH LCR activities and the sub-nuclear localization of the hGH locus.
This aim will utilize a series of transgenes that reflect a matrix of LCR activities to establish the linkages between LCR functions and sub-nuclear localization of the hGH locus. Significantly, the proposed studies will provide the P.I. the opportunity to fully exploit a set of time-intensive but highly informative mouse transgenic studies, broadening and strengthening his scientific capabilities in preparation for an independent career as an academic researcher ? ?
| Ho, Yugong; Tadevosyan, Aleksey; Liebhaber, Stephen A et al. (2008) The juxtaposition of a promoter with a locus control region transcriptional domain activates gene expression. EMBO Rep 9:891-8 |
| Shewchuk, Brian M; Ho, Yugong; Liebhaber, Stephen A et al. (2006) A single base difference between Pit-1 binding sites at the hGH promoter and locus control region specifies distinct Pit-1 conformations and functions. Mol Cell Biol 26:6535-46 |
| Ho, Yugong; Elefant, Felice; Liebhaber, Stephen A et al. (2006) Locus control region transcription plays an active role in long-range gene activation. Mol Cell 23:365-75 |
| Ho, Yugong; Liebhaber, Stephen A; Cooke, Nancy E (2004) Activation of the human GH gene cluster: roles for targeted chromatin modification. Trends Endocrinol Metab 15:40-5 |
