Chromosomal proteins from the embryoid body/teratocarcinoma system

Chromosomal proteins were isolated from simple embryoid bodies and teratocarcinomas, derivatives of the transplantable mouse testicular teratocarcinoma OTT-6050 of 129 mouse origin. The chromosomal proteins soluble in 5 M urea and low salt and the histones were extracted from embryoid body and teratocarcinoma chromatin. The use of long Laemmli (28-cm) gels enables a detailed comparison of the developmental changes in the 5 M urea-soluble chromosomal proteins which accumulate in the embryoid body and teratocarcinoma chromatin. The accumulated 5 M urea-soluble proteins above 30,000 daltons from embryoid body chromatin resolve into 69 stained bands and the corresponding group of proteins from teratocarcinomas resolves into 70 distinct bands. Both quantitative and qualitative differences at a minimum of 14 positions are detectable by visual inspection of the gels. Patterns of synthesis in the same group of proteins as assessed by two-dimensional polyacrylamide gel electrophoresis show marked changes during the developmental transition from an embryoid body to a teratocarcinoma. Twenty-eight major differences in the proteins synthesized during a 4-hr labeling period are detectable, with numerous minor differences evident on detailed inspection. Electrophoretic patterns of histones from the three stages of development indicate that histone 4 (H4) from teratomas is modified (acetylated) twice as much as H4 from embryoid bodies. The remaining histones do not show any detectable differences during the differentiation of embryoid bodies to teratocarcinomas. Thus, the differentiation process from embryoid bodies containing only endoderm and embryocarcinoma cells to teratocarcinomas containing a predominance of neuroepithelial cells appears to involve a large variation in synthesis of 5 M urea-soluble chromosomal proteins.