THE INTERFERON-STIMULABLE RESPONSE ELEMENTS OF 2 HUMAN GENES DETECT OVERLAPPING SETS OF TRANSCRIPTION FACTORS

Citation
J. Parrington et al., THE INTERFERON-STIMULABLE RESPONSE ELEMENTS OF 2 HUMAN GENES DETECT OVERLAPPING SETS OF TRANSCRIPTION FACTORS, European journal of biochemistry, 214(3), 1993, pp. 617-626
Citations number
44
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biology
ISSN journal
0014-2956
Volume
214
Issue
3
Year of publication
1993
Pages
617 - 626
Database
ISI
SICI code
0014-2956(1993)214:3<617:TIREO2>2.0.ZU;2-F
Abstract
We have previously reported three types of DNA-protein complexes, form ed specifically with the interferon-stimulable response elements (ISRE ) in the 5' flanking DNA of the interferon-inducible 6-16 and 9-27 gen es, a type-I interferon-inducible early complex involving factor E (IS GF3), M and G complexes induced more slowly in response to type-I and type-II interferons, respectively and CI/C2, a constitutive complex(s) . Similar complexes have been reported by others. The operationally de fined band-shift complexes M, G and CI/C2 are shown here to be heterog eneous and to differ in their factor content, depending on the ISRE pr obe. With a 9-27 ISRE probe the M, G and C1/C2 complexes all contain t he gamma subunit of ISGF3, which is present constitutively but is indu ced in response to IFN-alpha (to yield M) or IFN-gamma (to yield G). I n contrast, a 6-16 ISRE probe forms band-shift complexes with IFN-a-in ducible and IFN-gamma-inducible IRF1 and IRF2. With a 6-16 ISRE probe, therefore, M and G each correspond to two complexes which co-migrate in band-shift assays, one corresponding to IRF1, the other to IRF2. Wi th this probe, the constitutive complex C1/C2 corresponds predominantl y to IRF2. Consistent with this, IRF1 and IRF2 have lower affinity for the 9-27 ISRE than the 6-16 ISRE, whereas the reverse is true for E ( ISGF3) and its gamma subunit. Relatively small differences in affinity appear sufficient to determine whether or not a band-shift complex is detected. In the case of IRF1 and IRF2, the different affinities for the 6-16 and 9-27 probes are dominated by a dinucleotide sequence in t he centre of the 14-nucleotide 'score' ISRE. In contrast, preferential binding of E (ISGF3) by the 39-nucleotide 9-27 ISRE-containing sequen ce, although ISRE dependent, appears to be mediated by sequences 3' of the 'core' ISRE. Accordingly, these complexes can be simultaneously a ssayed using a hybrid probe consisting of the 5' flanking region and ' core' ISRE sequences from the 6 - 16 gene and sequences immediately 3' of the 'core' 9-27 ISRE sequence. No evidence was obtained for a modu latory role in factor binding for a pseudo-ISRE sequence close to ISRE in the 9-27 gene. The precise roles of IRF1 and IRF2 in the induction of IFN-beta and the control of interferon-inducible gene expression r emain to be established. Results from the analysis of the expression o f IRF1 and IRF2 in wild-type and mutant cells argue against a dominant negative role for unmodified IRF2.