Retinoic Acid-responsive Enhancers Located 3′ of the Hox A and Hox B Homeobox Gene Clusters

doi:10.1074/jbc.272.4.2167

Retinoic Acid-responsive Enhancers Located 3′ of the Hox A and Hox B Homeobox Gene Clusters

FUNCTIONAL ANALYSIS*

From the Department of Pharmacology, Cornell University Medical College, New York, New York 10021

^§ To whom correspondence should be addressed:
Dept. of Pharmacology, Cornell University Medical College, 1300 York Ave., New York, NY 10021
. Tel.: 212-746-6250; Fax: 212-746-8858.

Abstract

Homeobox genes control the spatial identity and differentiation of tissues in the developing vertebrate embryo. Retinoids are signaling molecules involved in the regulation of Hox genes. We previously identified a 3′ enhancer called the RAIDR₅, which contained a DR5 retinoic acid response element (RARE) and was responsible for the retinoic acid (RA)-associated expression of the murine Hoxa-1 gene in teratocarcinoma cells. We demonstrate that a similar enhancer, which contains a DR₅ RARE, is located at a DNase I-hypersensitive site 3′ of the murine Hoxb-1 gene. This enhancer, the Hoxb-1 RAIDR₅, regulates the RA responsiveness of the Hoxb-1 gene and is different in location and sequence from the RA-regulated 3′ Hoxb-1 enhancers previously described. Several DNA elements within the murine Hoxa-1 RA-inducible RAIDR₅ enhancer, including the DR₅ RARE, conserved element (CE) 1, and CE2, are conserved in the murine Hoxb-1 RAIDR₅ enhancer, the human homolog of Hoxa-1, and in the chicken Hoxb-1 gene. Gel shifts show that the CE2 sequence TATTTACTCA binds an RA-inducible factor, while UV cross-linking indicates that a 170-kDa protein binds to this sequence. Thus, the Hoxa-1 and Hoxb-1 genes possess 3′ enhancers with similar sequences through which their expression and responsiveness to endogenous retinoids are controlled.

Footnotes

↵^‡ Supported by a fellowship from the American Cancer Society PF4280 during a portion of this work.
↵* This work was supported in part by National Institutes of Health Grant R01CA39036 (L. J. G.). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) S78041[GenBank] (for murine Hoxa-1).
↵¹ The abbreviations used are:

Hox

homeobox

RA

retinoic acid

RARE

retinoic acid response element

RAR

retinoic acid receptor

RXR

retinoid X receptor

DR

direct repeat

DR₅

direct repeat 5

RAIDR₅

retinoic acid-inducible RARE direct repeat₅ enhancer

RAIDR₂

retinoic acid-inducible RARE direct repeat₂ enhancer

CE1

conserved element 1

CE2

conserved element 2

TK

thymidine kinase

CAT

chloramphenicol acetyltransferase

DTT

dithiothreitol

bp

base pair(s)

kb

kilobase pair(s).
↵² A. W. Langston and L. J. Gudas, unpublished observations.
- Received July 16, 1996.
- Revision received October 18, 1996.