Identification of a nuclear targeting signal in YopM from Yersinia spp.

YopM is a type III secretion effector from Yersinia which contributes to pathogenicity but whose action still remains unclear. It is an acidic, leucine-rich repeats (LRR) containing protein which migrates to the nucleus of target cells in spite of the fact that it does not contain any classical nuclear localization signal (NLS). Using a yeast approach, we observed that the three first LRRs (LRR1-3) and the 32 C-terminal residues of YopM (YopM(C-ter)) act as NLSs in yeast. Furthermore, by transfection of HEK293T cells, we observed that YopM(C-ter) could direct large recombinant EGFP-LexA-AD proteins into the nucleus of mammalian cells confirming that it contains a NLS. Critical residues for nuclear targeting were identified by site-directed mutagenesis in YOPMC-ter. In addition, we show that YOPMC-ter NLS is crucial for the nuclear targeting of an EGFP-YopM fusion protein. (C) 2004 Elsevier Ltd. All fights reserved.