The present invention provides methods and compostions to improve the efficiency of somatic cell nuclear transfer (SCNT) and the consequent production of nuclear transfer ESC (ntESC) and transgenic cells and/or non-human animals. More specifically, the present invention relates to the discovery that trimethylation of Histone H3-Lysine 9 (H3K9me3) in reprogramming resistant regions (RRRs) in the nuclear genetic material of donor somatic cells prevents efficient somatic cell nuclear reprogramming or SCNT. The present invention provide methods and compositions to decrease H3K9me3 in methods to improve efficacy of SCNT by exogenous or overexpression of the demethylase Kdm4 family and/or inhibiting methylation of H3K9me3 by inhibiting the histone methyltransferases Suv39h1 and/or Suv39h2.
