I will utilize our recently perfected microinjection procedure based on cell fusion, to study several aspects of genetic regulation. As a long-term project, we will microinject non-histone chromosomal proteins and small nuclear RNAs isolated from rat liver nuclei into undifferentiated cells and assay for the appearance of liver-specific proteins within undifferentiated cells. We will introduce I125-labeled histones into culture cells to study several aspects of histone-chromosome interaction. We will also conduct several projects involving microinjection of tRNA molecules. E. coli suppressor tRNA will be introduced into a collection of hypoxanthine-guanine phosphoribosyl transferase negative l-cell as an assay for nonsense mutations. Further, we will introduce tRNA molecules into SV40-transformed 3T3 cells to see if permissiveness for SV40 virus lytic infection is determined by specific tRNA molecules. Finally, we will introduce tRNA molecules into cells to determine whether elevated levels of tRNA influence the rate of tRNA biosynthesis.