RESUMEN
Transcriptional regulation of a gene is not always correlated with genetic information inherited from parents because the transcription of specific genes is often governed by the modification of chromatin structure. The study of transcriptional regulation by modifying chromatin structure is well-known as "epigenetics". Several methods involved in the modification of chromatin structure have been developed in the mammalian species during evolution. Among those methods, methylations of specific DNA region or histone are often used to control specific gene transcription. Therefore, understanding the activity of proteins involved in DNA or histone methylation is an initial step to control the transcriptional activity of a specific gene. Polycomb group (PcG) proteins were known to be repressors of transcription of a specific gene by creating and maintaining methylation or ubiquitination of the specific region of histone. Dependent on the target histone, the activity of PcG proteins effects on the development of specific lineage cells or the activity of specific cell types. In this review, the function, expression and activity of PcG proteins related with the development or activation of T cells are discussed.