Specific increase of perchloric acid extractable chromosomal proteins during mammalian erythropoiesis

1. 1. During the final stages of erythropoiesis in birds a novel histone, H5, is associated with chromatin condensation in the red blood cells. 2. 2. At a similar stage in mammalian erythropoiesis the chromatin also condenses prior to the loss of the red blood cell nuclei. 3. 3. Perchloric acid extraction of chromatin at this stage yields at least two proteins found in reduced amounts or not at all in control tissue. 4. 4. One of these proteins co-migrates electrophoretically with authentic H5 in an SDS-polyacrylamide gel, although this does not prove identity.