Intron-encoded homing endonuclease I-TevI also functions as a transcriptional autorepressor.
Customary binding sites of intron-encoded homing endonucleases lie within cognate intronless alleles, at the so-called homing sites. Here, we describe a novel, high-affinity binding site for I-TevI endonuclease, encoded within the group I td intron of phage T4. This site is an operator that overlaps the T4 late promoter, which drives I-TevI expression from within the td intron. I-TevI binds the operator and homing sites with equal affinity, and functions as a transcriptional autorepressor. Distinct sequence and spacing requirements of the catalytic domain result in reduced cleavage activity on operator DNA. Crystallographic studies showed that the overall interactions of the DNA-binding domain with the operator and homing sites are similar, but have some different hydrogen-bonding contacts. We present a model in which the flexibility in protein-DNA interactions allows I-TevI to bind variant intronless alleles to promote intron mobility while facilitating its function in autorepression, and thereby persistence in its host.
Edgell
David R
DR
Wadsworth Center, New York State Department of Health, Center for Medical Sciences, 150 New Scotland Avenue, Albany, New York 12208, USA.
Derbyshire
Victoria
V
Van Roey
Patrick
P
LaBonne
Stephen
S
Stanger
Matthew J
MJ
Li
Zhong
Z
Boyd
Thomas M
TM
Shub
David A
DA
Belfort
Marlene
M
D001483:Base Sequence; D018983:DNA Footprinting; D024202:Electrophoretic Mobility Shift Assay; D004706:Endodeoxyribonucleases / Q000235:genetics / Q000502:physiology*; D007438:Introns; D008969:Molecular Sequence Data; D009841:Oligonucleotides; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D012689:Sequence Homology, Nucleic Acid
D009841:Oligonucleotides; D012097:Repressor Proteins; D004706:Endodeoxyribonucleases; C065074:I-TEVI endonuclease