TY - JOUR
T1 - SRY and architectural gene regulation
T2 - The kinetic stability of a bent protein-DNA complex can regulate its transcriptional potency
AU - Ukiyama, Etsuji
AU - Jancso-Radek, Agnes
AU - Li, Biaoru
AU - Milos, Lukasz
AU - Zhang, Wei
AU - Phillips, Nelson B.
AU - Morikawa, Nobuyuki
AU - King, Chin Yen
AU - Chan, Ging
AU - Haqq, Christopher M.
AU - Radek, James T.
AU - Poulat, Francis
AU - Donahoe, Patricia K.
AU - Weiss, Michael A.
PY - 2001
Y1 - 2001
N2 - Protein-directed DNA bending is proposed to regulate assembly of higher-order DNA-multiprotein complexes (enhanceosomes and repressosomes). Because transcriptional initiation is a nonequilibrium process, gene expression may be modulated by the lifetime of such complexes. The human testis-determining factor SRY contains a specific DNA-bending motif, the high-mobility group (HMG) box, and is thus proposed to function as an architectural factor. Here, we test the hypothesis that the kinetic stability of a bent HMG box-DNA complex can in itself modulate transcriptional potency. Our studies employ a cotransfection assay in a mammalian gonadal cell line as a model for SRY-dependent transcriptional activation. Whereas sex-reversal mutations impair SRY-dependent gene expression, an activating substitution is identified that enhances SRY's potency by 4-fold. The substitution (l13F in the HMG box; fortuitously occurring in chimpanzees) affects the motif's cantilever side chain, which inserts between base pairs to disrupt base pairing. An aromatic F13 cantilever prolongs the lifetime of the DNA complex to an extent similar to its enhanced function. By contrast, equilibrium properties (specific DNA affinity, specificity, and bending; thermodynamic stability and cellular expression) are essentially unchanged. This correlation between potency and lifetime suggests a mechanism of kinetic control. We propose that a locked DNA bend enables multiple additional rounds of transcriptional initiation per promoter. This model predicts the occurrence of a novel class of clinical variants, bent but unlocked HMG box-DNA complexes with native affinity and decreased lifetime. Aromatic DNA-intercalating agents exhibit analogous kinetic control of transcriptional elongation whereby chemotherapeutic potencies correlate with drug-DNA dissociation rates.
AB - Protein-directed DNA bending is proposed to regulate assembly of higher-order DNA-multiprotein complexes (enhanceosomes and repressosomes). Because transcriptional initiation is a nonequilibrium process, gene expression may be modulated by the lifetime of such complexes. The human testis-determining factor SRY contains a specific DNA-bending motif, the high-mobility group (HMG) box, and is thus proposed to function as an architectural factor. Here, we test the hypothesis that the kinetic stability of a bent HMG box-DNA complex can in itself modulate transcriptional potency. Our studies employ a cotransfection assay in a mammalian gonadal cell line as a model for SRY-dependent transcriptional activation. Whereas sex-reversal mutations impair SRY-dependent gene expression, an activating substitution is identified that enhances SRY's potency by 4-fold. The substitution (l13F in the HMG box; fortuitously occurring in chimpanzees) affects the motif's cantilever side chain, which inserts between base pairs to disrupt base pairing. An aromatic F13 cantilever prolongs the lifetime of the DNA complex to an extent similar to its enhanced function. By contrast, equilibrium properties (specific DNA affinity, specificity, and bending; thermodynamic stability and cellular expression) are essentially unchanged. This correlation between potency and lifetime suggests a mechanism of kinetic control. We propose that a locked DNA bend enables multiple additional rounds of transcriptional initiation per promoter. This model predicts the occurrence of a novel class of clinical variants, bent but unlocked HMG box-DNA complexes with native affinity and decreased lifetime. Aromatic DNA-intercalating agents exhibit analogous kinetic control of transcriptional elongation whereby chemotherapeutic potencies correlate with drug-DNA dissociation rates.
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U2 - 10.1210/mend.15.3.0621
DO - 10.1210/mend.15.3.0621
M3 - Article
C2 - 11222738
AN - SCOPUS:85047683884
SN - 0888-8809
VL - 15
SP - 363
EP - 377
JO - Molecular Endocrinology
JF - Molecular Endocrinology
IS - 3
ER -