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Molecular and Cellular Biology, January 2000, p. 91-103, Vol. 20, No. 1
Department of Biochemistry, Dartmouth Medical
School, Hanover, New Hampshire 03755,1 and
Huntsman Cancer Institute, University of Utah, Salt Lake City,
Utah 84112-55502
Received 15 June 1999/Returned for modification 22 July
1999/Accepted 4 October 1999
Core-binding factor
0270-7306/0/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Auto-Inhibition and Partner Proteins, Core-Binding
Factor
(CBF
) and Ets-1, Modulate DNA Binding by CBF
2
(AML1)
2 (CBF
2; otherwise known as AML1 or
PEBP2
B) is a DNA-binding subunit in the family of core-binding factors (CBFs), heterodimeric transcription factors that play pivotal
roles in multiple developmental processes in mammals, including
hematopoiesis and bone development. The Runt domain in CBF
2 (amino
acids 51 to 178) mediates DNA binding and heterodimerization with the
non-DNA-binding CBF
subunit. Both the CBF
subunit and the
DNA-binding protein Ets-1 stimulate DNA binding by the CBF
2 protein.
Here we quantify and compare the extent of cooperativity between
CBF
2, CBF
, and Ets-1. We also identify auto-inhibitory sequences
within CBF
2 and sequences that modulate its interactions with CBF
and Ets-1. We show that sequences in the CBF
2 Runt domain and
sequences C terminal to amino acid 214 inhibit DNA binding. Sequences C
terminal to amino acid 214 also inhibit heterodimerization with the
non-DNA-binding CBF
subunit, particularly heterodimerization off
DNA. CBF
rescinds the intramolecular inhibition of CBF
2, stimulating DNA binding approximately 40-fold. In comparison, Ets-1
stimulates CBF
2 DNA binding 7- to 10-fold. Although the Runt domain
alone is sufficient for heterodimerization with CBF
, sequences N
terminal to amino acid 41 and between amino acids 190 and 214 are
required for cooperative DNA binding with Ets-1. Cooperative DNA
binding with Ets-1 is less pronounced with the CBF
2-CBF
heterodimer than with CBF
2 alone. These analyses demonstrate that
CBF
2 is subject to both negative regulation by intramolecular interactions, and positive regulation by two alternative partnerships.
*
Corresponding author. Mailing address: Department of
Biochemistry, Dartmouth Medical School, Hanover, NH 03755. Phone: (603) 650-1159. Fax: (603) 650-1128. E-mail:
Nancy.Speck{at}dartmouth.edu.
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