Structure-specific DNA-binding proteins as the foundation for three-dimensional chromatin organization.
Any functions of tandem repetitive sequences need proteins that specifically bind to them. Telomere-binding TRF2/MTBP attaches telomeres to the nuclear envelope in interphase due to its rod-domain-like motif. Interphase nuclei organized as a number of sponge-like ruffly round chromosome territories that could be rotated from outside. SAF-A/hnRNP-U and p68-helicase are proteins suitable to do that. Their location in the interchromosome territory space, ATPase domains, and the ability to be bound by satellite DNAs (satDNA) make them part of the wires used to help chromosome territory rotates. In case of active transcription p68-helicase can be involved in the formation of local "gene expression matrices" and due to its satDNA-binding specificity cause the rearrangement of the local chromosome territory. The marks of chromatin rearrangement, which have to be heritable, could be provided by SAF-A/hnRNP-U. During telophase unfolding the proper chromatin arrangement is restored according to these marks. The structural specificity of both proteins to the satDNAs provides a regulative but relatively stable mode of binding. The structural specificity of protein binding could help to find the "magic" centromeric sequence. With future investigations of proteins with the structural specificity of binding during early embryogenesis, when heterochromatin formation goes on, the molecular mechanisms of the "gene gating" hypothesis (Blobel, 1985) will be confirmed.
Institute of Cytology, Russian Academy of Sciences, St. Petersburg 194064, Russia.
O I
OI
Podgornaya
A P
AP
Voronin
N I
NI
Enukashvily
I V
IV
Matveev
I B
IB
Lobov
D000818:Animals; D002843:Chromatin / Q000235:genetics / Q000648:ultrastructure*; D053487:DEAD-box RNA Helicases; D004268:DNA-Binding Proteins / Q000235:genetics / Q000648:ultrastructure*; D005057:Eukaryotic Cells / Q000166:cytology / Q000378:metabolism*; D034722:Heterogeneous-Nuclear Ribonucleoprotein U / Q000235:genetics; D006801:Humans; D015530:Nuclear Matrix / Q000235:genetics / Q000648:ultrastructure*; D011494:Protein Kinases / Q000235:genetics; D020365:RNA Helicases / Q000235:genetics; D035341:Telomeric Repeat Binding Protein 2 / Q000235:genetics
D002843:Chromatin; D004268:DNA-Binding Proteins; D034722:Heterogeneous-Nuclear Ribonucleoprotein U; D035341:Telomeric Repeat Binding Protein 2; D011494:Protein Kinases; C506749:Ddx5 protein, human; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases