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2 15 leucinezippertranscriptionfactors

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Unformatted text preview: ithout separating nucleotides nucleotides bZIP is similar to DNA-binding bZIP structure of dimerized bHLH proteins proteins some proteins, such as Myc have some hybrid bHLH-ZIP domains where hybrid leu zipper stabilizes bHLH dimer leu Weaver 2002 Molecular Biology Ed. 2 15 LEUCINE ZIPPER TRANSCRIPTION FACTORS LEUCINE ZIPPER TRANSCRIPTION FACTORS • • • • Leucine zippers form homo- or heterodimers eg. Fos & Jun dimerization to form AP1 transcription factor, Fos orginally identified as SV40 enhancer binding protein orginally Fos and Jun are encoded by the cellular counterparts, c-fos & cFos c-fos cjun, of the oncogenes v-fos & v-jun found in murine and avian jun, v-fos sarcoma viruses, respectively sarcoma Jun/Jun binds AP1 site 10X lower affinity than Jun/Fos (Fos cannot Jun/Jun form homodimers) form 16 CHROMATIN & GENE EXPRESSION CHROMATIN & GENE EXPRESSION • Transcription factors do not interact with naked DNA Transcription chromosome organization of eukaryotic DNA has direct effects on transcription regulation: effects • (1) DNA packaging - transcription can be repressed (1) when DNA coiled into nucleosomes when • (2) Chromosomal domains - large regions of DNA (2) organized into regulatory domain organized • (3) DNA methylation & imprinting - methylated DNA is (3) generally not expressed generally 17 (1) DNA PACKAGING & TRANSCRIPTION: HISTONES (1) DNA PACKAGING & TRANSCRIPTION: HISTONES • Eukaryotes: DNA packaged Eukaryo...
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