We have compared HMG1 with the product of tryptic removal of its acidic C-terminal domain termed HMG3, which contains two 'HMG-box' DNA-binding domains. (i) HMG3 has a higher affinity for DNA than HMG1. (ii) Both HMG1 and HMG3 supercoil circular DNA in the presence of topoisomerase I. Supercoiling by HMG3 is the same at approximately 50 mM and approximately 150 mM ionic strength, as is its affinity for DNA, whereas supercoiling by HMG1 is less at 150 mM than at 50 mM ionic strength although its affinity for DNA is unchanged, showing that the acidic C-terminal tail represses supercoiling at the higher ionic strength. (iii) Electron microscopy shows that HMG3 at a low protein:DNA input ratio (1:1 w/w; r = 1), and HMG1 at a 6-fold higher ratio, cause looping of relaxed circular DNA at 150 mM ionic strength. Oligomeric protein 'beads' are apparent at the bases of the loops and at cross-overs of DNA duplexes. (iv) HMG3 at high input ratios (r = 6), but not HMG1, causes DNA compaction without distortion of the B-form. The two HMG-box domains of HMG1 are thus capable of manipulating DNA by looping, compaction and changes in topology. The acidic C-tail down-regulates these effects by modulation of the DNA-binding properties.

• MeSH
• cirkulární dichroismus MeSH
• DNA-topoisomerasy I metabolismus   MeSH
• DNA chemie   metabolismus   MeSH
• elektronová mikroskopie MeSH
• konformace nukleové kyseliny * MeSH
• osmolární koncentrace MeSH
• peptidové fragmenty chemie   metabolismus   MeSH
• proteiny s vysokou pohyblivostí chemie   metabolismus   MeSH
• skot MeSH
• superhelikální DNA metabolismus   MeSH
• trypsin metabolismus   MeSH
• vazebná místa MeSH
• zvířata MeSH
• Check Tag
• skot MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA-topoisomerasy I MeSH
• DNA MeSH
• peptidové fragmenty MeSH
• proteiny s vysokou pohyblivostí MeSH
• superhelikální DNA MeSH
• trypsin MeSH