TRIM28 and breast cancer: However, these findings apparently differ from previous reports: TRIM28 and sumoylated TRIM28 have been reported to be transcriptional co-repressors of ZBRK1, a zinc-finger DNA-binding protein that mediates transcriptional repression of a few p53 downstream genes43; when ZBRK1 is overexpressed, the N-terminal SUMO1-TRIM28 in-frame fusion protein can suppress doxorubicin-induced p21 promoter activation in the MCF-7 breast cancer cell line44.