In this study, we characterized SUB1 expression specifically in aggressive prostate cancer. Yeast SUB1 is biochemically identified as a stimulator of in vitro basal transcription that binds to single-strand DNA in the regions of transcription initiation.17, 18 SUB1 is a nuclear protein and is shown to have a role in various cellular processes.19, 20, 21, 22, 23, 24 It is substituted for replication protein A during transcription elongation.25 In addition to its role as transcriptional coactivator, SUB1 has been shown to repress promoter-driven transcription as well as nonspecific transcription in vitro.26, 27 Studies have reported that SUB1 interacts with distinct domains of activators such as VP16, GAL4, AP2, HIV-TAT, P53 and SMYD3 to modulate their functions.19, 22, 28, 29, 30, 31, 32 Previous studies indicated that the overexpression of SUB1 in a population of normal dermal multipotent fibroblasts resulted in the tumorigenic transformation of the cells, indicating its role in tumorigenesis. SUB1 has been recently found to show an upregulated level in different cancers. Expression of SUB1 was correlated with the levels of VEGF-C, VEGF-D and VEGFR-3 during the development of lymphangiogenesis and lymphatic metastasis in lung adenocarcinoma.33 SUB1 is also shown to have a role in non-small-cell lung cancer34 and astrocytoma.35 A recent study demonstrated that SUB1 has a role in SMYD3-mediated transactivation of growth/invasion-stimulatory genes in cancer cells.32