Acts as component of the CCR4-NOT core complex, which in the nucleus seems to be a general transcription factor, and in the cytoplasm the major mRNA deadenylase involved in mRNA turnover. NOT2 is required for the integrity of the complex. The NOT protein subcomplex negatively regulates the basal and activated transcription of many genes. Preferentially affects TC-type TATA element-dependent transcription. Could directly or indirectly inhibit component(s) of the general transcription machinery.