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Molecular and Cellular Biology, May 2001, p. 3387-3397, Vol. 21, No. 10
0270-7306/01/$04.00+0   DOI: 10.1128/MCB.21.10.3387-3397.2000
Copyright © 2001, American Society for Microbiology. All rights reserved.

JAK2 Activates TFII-I and Regulates Its Interaction with Extracellular Signal-Regulated Kinase

Dae-Won Kim and Brent H. Cochran*

Department of Cellular and Molecular Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111

Received 10 January 2001/Accepted 14 February 2001

TFII-I is a transcription factor that shuttles between the cytoplasm and nucleus and is regulated by serine and tyrosine phosphorylation. Tyrosine phosphorylation of TFII-I can be regulated in a signal-dependent manner in various cell types. In B lymphocytes, Bruton's tyrosine kinase has been identified as a TFII-I tyrosine kinase. Here we report that JAK2 can phosphorylate and regulate TFII-I in nonlymphoid cells. The activity of TFII-I on the c-fos promoter in response to serum can be abolished by dominant negative JAK2 or the specific JAK2 kinase inhibitor AG490. Consistent with this, we have also found that JAK2 is activated by serum stimulation of fibroblasts. Tyrosine 248 of TFII-I is phosphorylated in vivo upon serum stimulation or JAK2 overexpression, and mutation of tyrosine 248 to phenylalanine inhibits the ability of JAK2 to phosphorylate TFII-I in vitro. Tyrosine 248 of TFII-I is required for its interaction with and phosphorylation by ERK and its in vivo activity on the c-fos promoter. These results indicate that the interaction between TFII-I and ERK, which is essential for its activity, can be regulated by JAK2 through phosphorylation of TFII-I at tyrosine 248. Thus, like the STAT factors, TFII-I is a direct substrate of JAK2 and a signal-dependent transcription factor that integrates signals from both tyrosine kinase and mitogen-activated protein kinase pathways to regulate transcription.

* Corresponding author. Mailing address: Department of Cellular and Molecular Physiology, Tufts University School of Medicine, 136 Harrison Ave., Boston, MA 02111. Phone: (617) 636-0442. Fax: (617) 636-6745. E-mail: cochran{at}opal.tufts.edu.

Molecular and Cellular Biology, May 2001, p. 3387-3397, Vol. 21, No. 10
0270-7306/01/$04.00+0   DOI: 10.1128/MCB.21.10.3387-3397.2000
Copyright © 2001, American Society for Microbiology. All rights reserved.


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