Using MMTV to discover new genes that are important for breast cancer

The mouse mammary tumor virus (MMTV) is transmitted from mother to pup during nursing.  The virus integrates its own genetic information into the mouse genome and causes breast cancer.  By integrating viral DNA into specific locations of mouse chromosomes, certain cancer-promoting genes (oncogenes) can become corrupted and activated.  We can therefore use MMTV to find what genes are important for promoting cancer in mice and translate that new knowledge into understanding breast cancer in humans.

Investigating the function of ZC3H8

Our work has been focused on one gene of interest, ZC3H8, and associated pathways important for cell biology, molecular biology, and cancer biology.  We found that cells with high expression of ZC3H8 have aggressive oncogenic properties while cells with reduced expression have less aggressive properties.  ZC3H8 encodes for a protein that contains three CCCH non-classical zinc finger motifs that may bind to mRNA in the nucleus.  Disruption of these domains by DNA mutagenesis results in a protein that lacks the aggressive features of the wild type protein.  We are currently investigating the role of these zinc finger motifs in the overall function, mRNA binding, and localization of Zc3h8 in cells.

Exploring the regulation of Zc3h8

Zc3h8 protein contains a sequence that is known to be phosphorylated by casein kinase 2 (CK2) – an important signaling molecule in cancer and cell growth.  Zc3h8 function is sensitive to various inhibitors of CK2 indicating the importance of phosphorylation in the regulation of Zc3h8.  Furthermore, mutations to Zc3h8 that either prevent phosphorylation or act as constitutively phosphorylated have dramatic changes on cells growing in vitro and tumors in vivo.  We are studying the role of phosphorylation and other potential binding partners in how Zc3h8 is regulated and promotes or prevents cell proliferation and migration.

Localization of Zc3h8 to nuclear PML and Cajal Bodies

Using confocal microscopy, we found that Zc3h8 is localized to the nucleus of cells and is mostly found in discrete foci that are also the location of promyelocytic leukemia protein (PML) and Cajal Body markers.  These nuclear domains are known for regulating RNA modification, transcription, DNA damage repair, and many known tumor suppressor genes.  We are using imaging methods and molecular biology to determine what factors contribute to Zc3h8 localization and what role it plays at these important nuclear regulatory sites.