The C-terminal extension (CTE) of the nuclear hormone receptor DNA binding domain determines interactions and functional response to the HMGB-1/-2 co-regulatory proteins.
Previously, we and others reported that the high mobility group proteins, HMGB-1/-2, enhance DNA binding in vitro and transactivation in situ by the steroid hormone subgroup of nuclear receptors but did not influence these functions of class II receptors. We show here that the DNA binding domain (DBD) is sufficient to account for the selective influence of HMGB-1/-2 on the steroid class of receptors. Furthermore, the use of chimeric DBDs reveals that this selectivity is dependent on the C-terminal extension (CTE), amino acid sequences adjacent to the zinc finger core DBD. HMGB-1/-2 interact directly with the DBDs of steroid but not class II receptors, and this interaction requires the CTE. This in vitro interaction correlates with a requirement of the CTE for maximal HMGB-1/-2 enhancement of DNA binding in vitro and transcriptional activation in cells. Finally, class II receptor DBDs have a much higher intrinsic affinity for DNA than steroid receptor DBDs, and this affinity difference is also dependent on the CTE. These results reveal the importance of the steroid receptor CTE for DNA binding affinity and functional response to HMGB-1/-2.
Melvin
Vida Senkus
VS
Program in Molecular Biology and the Department of Pharmacology, University of Colorado Health Sciences Center, Denver 80262, USA.
Roemer
Sarah C
SC
Churchill
Mair E A
ME
Edwards
Dean P
DP
D000595:Amino Acid Sequence; D001483:Base Sequence; D004247:DNA / Q000378:metabolism*; D017931:DNA Primers; D024243:HMGB1 Protein / Q000378:metabolism*; D024261:HMGB2 Protein / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism
D017931:DNA Primers; D024243:HMGB1 Protein; D024261:HMGB2 Protein; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D004247:DNA