PT  - JOURNAL ARTICLE
AU  - Flanagan, Thomas W.
AU  - Files, Jacob K.
AU  - Casano, Kelsey Rose
AU  - George, Eric M.
AU  - Brown, David T.
TI  - Photobleaching studies reveal that a single amino acid polymorphism is responsible for the differential binding affinities of linker histone subtypes H1.1 and H1.5
AID  - 10.1242/bio.016733
DP  - 2016 Mar 15
TA  - Biology Open
PG  - 372--380
VI  - 5
IP  - 3
4099  - http://bio.biologists.org/content/5/3/372.short
4100  - http://bio.biologists.org/content/5/3/372.full
SO  - Biology Open2016 Mar 15; 5
AB  - Mammals express six major somatic linker histone subtypes, all of which display dynamic binding to chromatin, characterized by transient binding at a given location followed by rapid translocation to a new site. Using photobleaching techniques, we systematically measured the exchange rate of all six mouse H1 subtypes to determine their relative chromatin-binding affinity. Two subtypes, H1.1 and H1.2, display binding affinities that are significantly lower than all other subtypes. Using in vitro mutagenesis, the differences in chromatin-binding affinities between H1.1 (lower binding affinity) and H1.5 (higher binding affinity) were mapped to a single amino acid polymorphism near the junction of the globular and C-terminal domains. Overexpression of H1.5 in density arrested fibroblasts did not affect cell cycle progression after release. By contrast, overexpression of H1.1 resulted in a more rapid progression through G1/S relative to control cells. These results provide structural insights into the proposed functional significance of linker histone heterogeneity.