METHANOBACTERIUM-FORMICICUM, A MESOPHILIC METHANOGEN, CONTAINS 3 HFO HISTONES

The mesophilic methanogen Methanobacterium formicicum JF-1 has been sh own to contain three members of the HMf family of archaeal histones, d esignated HFoA1, HFoA2, and HFoB, and their encoding genes (hfoA1, hfo A2, and hfoB) have been cloned and sequenced, The HFo histones have pr imary sequences that are 75 to 82% identical to the HMf sequences and appear to share ancestry with the core histones that form the eukaryal nucleosome, The HFo proteins bind and compact DNA molecules into nucl eosome-like structures apparently identical to those formed by the HMf proteins, but, in contrast to the HMf proteins, this activity of the HFo proteins is lost after incubation at 95 degrees C for 5 h.