Xin Dong


The cluster determinant 4 (CD4) molecule is a transmembrane glycoprotein. CD4 is essential for normal T helper cell function and plays an important role in T cell development and activation. CD4 is encoded by a single gene located on chromosome 6 in the mouse and chromosome 12 in the human. Both human and murine CD4 genes are divided into ten exons spanning more than 25 kb and have a large non-coding region in the first and third intron. CD4 gene expression is controlled primarily at the transcriptional level during T cell development and activation.

An enhancer has been identified approximately 13 kb 5' of the transcriptional start site of the murine CD4 gene. A comparison of the DNA regions around and within the mouse CD4 enhancer with that of the human CD4 enhancer region reveals 11 regions of homology. There is also a DNase I hypersensitive (DH) site located immediately upstream of the 5' enhancer. These data suggest that the enhancer may be a part of a larger control element of deletions (3' and 5' direction) covering a 1158 bp region containing the enhancer and the 5' DH site were engineered using the Bal 31 deletion method and then analyzed using the transient transfection, chloramphenicol acetyltransferase (CAT) assay. Two novel cis-acting elements with silencer function were discovered by Bal 31 deletions. Their silencer functions were further confirmed by subcloning them at different positions and different orientations relative to CD4 promoter. These subcloned constructs were tested for function in transient transfection and CAT assays. Furthermore these two cis-acting elements were also analyzed with the electrophoretic mobility shift assay for their ability to bind cell-specific nuclear proteins. In addition, the potential binding sites for transcriptional factors within these novel cis-acting elements were identified by the DNase I footprinting technique.

LLU Discipline





Graduate School

First Advisor

R. Bruce Wilcox

Second Advisor

Istvan Fodor

Third Advisor

William H. R. Langridge

Fourth Advisor

Thomas Linkhart

Fifth Advisor

Aladar A. Szalay

Degree Name

Doctor of Philosophy (Medical Science)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Antigens, CD4; Antigens -- immunology; Glycoproteins; Reverse Transcriptions



Page Count

xx: 208

Digital Format


Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.


Loma Linda University Electronic Theses and Dissertations

Collection Website


Loma Linda University. Del E. Webb Memorial Library. University Archives