In vitro and in vivo characterization of coactivator acetyltransferases in transcription regulation.

Format:

Book

Thesis/Dissertation

Author/Creator:

Liu, Lin.

Contributor:

Sharp, Kim, 1973- advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Molecular biology.

0307.

Penn dissertations--Biochemistry.

Biochemistry--Penn dissertations.

Penn dissertations--Molecular biophysics.

Molecular biophysics--Penn dissertations.

Local Subjects:

Penn dissertations--Biochemistry.

Biochemistry--Penn dissertations.

Penn dissertations--Molecular biophysics.

Molecular biophysics--Penn dissertations.

0307.

Physical Description:

125 pages

Contained In:

Dissertation Abstracts International 60-04B.

System Details:

Mode of access: World Wide Web.

text file

Summary:

Extensive studies have been done on the mechanism of gene activation using nonchromosomal DNA. However, how transcription activation is carried out on the highly compacted chromatin template in vivo remains elusive. It has been suggested that histone acetylation is involved in chromatin remodeling which may play a role in facilitating the binding of transcription factors to chromatin templates. Hyperacetylation of histones has also been a hallmark of transcription within active regions on chromatin. Recently, yeast GCN5 protein, originally identified as a transcriptional coactivator, was demonstrated to be a histone acetyltransferase (HAT). This discovery provided a direct mechanistic link between chromatin remodeling and transcription activation. However, it is not known whether the. acetylase activity of GCN5 is crucial for its function as a transcription cofactor. To address this question, an extensive alanine-scan mutagenesis analysis of the GCN5 HAT domain was performed. We found that mutations that disrupted the HAT activity of GCN5 also abolished GCN5's ability to potentiate transcriptional activation in vivo. This study clearly demonstrated that the acetylase activity of GCN5 is indispensable for its function as a transcription coactivator. Meanwhile, a number of other coactivators have been shown to possess intrinsic acetyltransferase activity. They display great diversity in transcriptional regulation as well as in their substrate specificities on histones and nucleosomes. In addition to their roles in acetylating histones, some HATs exhibit the ability to acetylate transcription factors. We have demonstrated that the coactivator acetyltransferase PCAF, a human GCN5 homolog, is able to acetylate p53, which is a tumor suppressor and transcription activator protein. The acetylation of p53 by PCAF in vitro was found to significantly enhance the ability of p53 to bind to DNA. Importantly, p53 has been determined to be acetylated at the same site in vivo upon UV or ionizing radiation stimulation. These in vitro and in vivo studies of coactivator acetyltransferases suggest multiple levels of transcription regulation provided by these modifications. Acetylation may have general effects in gene activation that are at least partially performed by coactivator acetyltransferases.

Notes:

Thesis (Ph.D. in Biochemistry and Molecular biophysics) -- University of Pennsylvania, 1999.

Source: Dissertation Abstracts International, Volume: 60-04, Section: B, page: 1443.

Adviser: Kim Sharp.

Local Notes:

School code: 0175.

ISBN:

9780599259294

Access Restriction:

Restricted for use by site license.