Ki-67 protein is associated with ribosomal RNA transcription in quiescent and proliferating cells

✍ Scribed by Jörn Bullwinkel; Bettina Baron-Lühr; Anja Lüdemann; Claudia Wohlenberg; Johannes Gerdes; Thomas Scholzen

• Book ID: 102882519
• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 720 KB
• Volume: 206
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.20494

✦ Synopsis

Abstract

The nuclear Ki‐67 protein (pKi‐67) has previously been shown to be exclusively expressed in proliferating cells. As a result, antibodies against this protein are widely used as prognostic tools in cancer diagnostics. Here we show, that despite the strong downregulation of pKi‐67 expression in non‐proliferating cells, the protein can nevertheless be detected at sites linked to ribosomal RNA (rRNA) synthesis. Although this finding does not argue against the use of pKi‐67 as a proliferation marker, it has wide ranging implications for the elucidation of pKi‐67 function. Employing the novel antibody TuBB‐9, we could further demonstrate that also in proliferating cells, a fraction of pKi‐67 is found at sites linked to the rRNA transcription machinery during interphase and mitosis. Moreover, chromatin immunoprecipitation (ChIP) assays provided evidence for a physical association of pKi‐67 with chromatin of the promoter and transcribed region of the rRNA gene cluster. These data strongly suggest a role for pKi‐67 in the early steps of rRNA synthesis. © 2005 Wiley‐Liss, Inc.