TFII-I is a multifunctional transcription factor that is also involved in signal transduction. Here we show that TFII-I undergoes a c-Src-dependent tyrosine phosphorylation on tyrosine residues 248 and 611 and translocates to the nucleus in response to growth factor signaling. Tyrosine-phosphorylated nuclear TFII-I activates a stably integrated c-fos reporter gene. Withdrawal of signal leads to diminution of nuclear TFII-I, suggesting that the signal-dependent translocation is reversible. Antibodies against either TFII-I or c-Src abrogate growth factor-stimulated activation of c-fos. Consistent with the notion that tyrosine phosphorylation of TFII-I is required for its transcriptional activity, phosphorylation-deficient mutants of TFII-I fail to activate the c-fos promoter. These data demonstrate that TFII-I, through a Src-dependent mechanism, reversibly translocates from the cytoplasm to the nucleus, leading to the transcriptional activation of growth-regulated genes.Extracellular signals are ultimately transduced to the nucleus through a series of complicated biochemical steps that result in the activation of specific genes. Inducible transcription factors often play a critical role in this process by responding to the cell's external signals. Here we demonstrate that the multifunctional transcription factor TFII-I is activated in response to extracellular signals, translocates into the nucleus, and thus links signal transduction events to transcription.Based on its unique interactions at both a core promoter element and upstream regulatory sites, TFII-I is postulated to be a novel transcription factor that facilitates communication between upstream regulatory proteins and the basal machinery (1-3). There are four alternatively spliced isoforms of TFII-I, all of which are characterized by the presence of six I repeats, R1ϪR6, each containing a potential helix-loop-helix motif implicated in protein-protein interactions (4, 5). Recent genetic and biochemical data also indicate that TFII-I belongs to a family of protein characterized by the presence of I-repeat, first identified in TFII-I (6). Besides its transcription functions, TFII-I is shown to be phosphorylated at both serine/threonine and tyrosine residues, and tyrosine phosphorylation is critical for its transcriptional activity (7). Furthermore, it has been shown that a variety of growth-related signals lead to enhanced tyrosine phosphorylation and increased transcriptional activity of TFII-I (7, 8). In the B-cell cytoplasm, a large fraction of TFII-I is associated constitutively with Bruton's tyrosine kinase (9, 10). TFII-I is tyrosine-phosphorylated by Bruton's tyrosine kinase in vitro (10), and upon immunoglobulin receptor cross-linking in B cells, TFII-I is released from Bruton's tyrosine kinase to enter the nucleus (9). Thus, mutations impairing the association between TFII-I and Bruton's tyrosine kinase may result in improper TFII-I localization, activation, and diminished transcription, leading to defective B-cell function (9).Whereas TFII-I appear...

The multifunctional transcription factor TFII-I is tyrosine phosphorylated in response to extracellular growth signals and transcriptionally activates growth-promoting genes. However, whether activation of TFII-I also directly affects the cell cycle profile is unknown. Here we show that under normal growth conditions, TFII-I is recruited to the cyclin D1 promoter and transcriptionally activates this gene. Most strikingly, upon cell cycle arrest resulting from genotoxic stress and p53 activation, TFII-I is ubiquitinated and targeted for proteasomal degradation in a p53-and ATM (ataxia telangiectasia mutated)-dependent manner. Consistent with a direct role of TFII-I in cell cycle regulation and cellular proliferation, stable and ectopic expression of wild-type TFII-I increases cyclin D1 levels, resulting in accelerated entry to and exit from S phase, and overcomes p53-mediated cell cycle arrest, despite radiation. We further show that the transcriptional regulation of cyclin D1 and cell cycle control by TFII-I are dependent on its tyrosine phosphorylation at positions 248 and 611, sites required for its growth signal-mediated transcriptional activity. Taken together, our data define TFII-I as a growth signal-dependent transcriptional activator that is critical for cell cycle control and proliferation and further reveal that genotoxic stress-induced degradation of TFII-I results in cell cycle arrest.

Bright/ARID3a/Dril1, a member of the ARID family of transcription factors, is expressed in a highly regulated fashion in B lymphocytes, where it enhances immunoglobulin transcription three-to sixfold. Recent publications from our lab indicated that functional, but not kinase-inactive, Bruton's tyrosine kinase (Btk) is critical for Bright activity in an in vitro model system, yet Bright itself is not appreciably tyrosine phosphorylated. These data suggested that a third protein, and Btk substrate, must contribute to Bright-enhanced immunoglobulin transcription. The ubiquitously expressed transcription factor TFII-I was identified as a substrate for Btk several years ago. In this work, we show that TFII-I directly interacts with human Bright through amino acids in Bright's protein interaction domain and that specific tyrosine residues of TFII-I are essential for Bright-induced activity of an immunoglobulin reporter gene. Moreover, inhibition of TFII-I function in a B-cell line resulted in decreased heavy-chain transcript levels. These data suggest that Bright functions as a three-component protein complex in the immunoglobulin locus and tie together previous data indicating important roles for Btk and TFII-I in B lymphocytes.The transcription factor Bright (B-cell regulator of immunoglobulin H [IgH] transcription)/ARID3a/Dril1 is a B-cellspecific protein first discovered in a mature mouse B-cell line, BCg3R1-d, as a mobility-shifted protein complex that caused three-to sixfold increases in heavy-chain mRNA levels in response to stimulation with a T-dependent antigen and interleukin-5 (42, 43). Bright binds to AϩT-rich regions of the intronic heavy-chain enhancer previously identified as matrix association regions and to regions 5Ј of some variable heavychain (V H ) promoters, including the V1 S107 family gene (15,43). The cDNA for Bright was isolated in 1995, and the protein was shown to interact with DNA as a multimeric complex that included multiple copies of Bright (15). The Bright protein structure consists of an acidic N-terminal domain of unknown function, a DNA-binding AϩT-rich interaction domain (ARID), a putative transactivation domain, a protein interaction domain containing a helix-turn-helix region, and a small carboxyl-terminal domain with no assigned function.Earlier studies indicated that Bruton's tyrosine kinase (Btk), the defective enzyme in X-linked immunodeficiency disease in both mice and humans, is a component of the Bright DNAbinding complex (28, 44). X-linked immunodeficiency disease in mice, or X-linked agammaglobulinemia (XLA) in humans, results in blocks in B-lymphocyte development that ultimately lead to a deficient production of serum antibodies (9,33,40). Patients with XLA are unable to fight normal bacterial infections without frequent intravenous Ig treatments. Although Btk was identified as the genetic defect in XLA many years ago, the mechanism by which Btk deficiencies lead to early blocks at the pro-B-to pre-B-lymphocyte stages in humans remains unclear.Recently, an in vitro mode...

Reproduction, or the faithful passage of genetic information from one cell to its progeny, is central to life. To achieve reproduction faithfully cells have developed the cell cycle during which error-free replication of DNA, followed by division of the nucleus and partitioning of the cytoplasm yields two daughter cells. Prior to committing to reproduction, cells must sense mitogen levels in their environment and transduce those signals to the nucleus through a series of biochemical steps, resulting in spatial and/or temporal activation of genes that will drive cell cycle progression past the restriction point and initiate DNA replication. One way external signals are transmitted to the nucleus is via mitogen inducible transcription factors that shuttle between the cytoplasm and nucleus. Here we introduce a newly discovered pathway by which TFII-I, a growth signal induced transcription factor, operates in the prerestriction point and mitogen dependent phase of the cell cycle. We also discuss a potential role for TFII-I in DNA repair and how it might be involved in signal dependent DNA repair versus cell cycle.

A man in his mid-40s presented to the emergency department with three weeks of early satiety, epigastric pain, nausea, vomiting, a 15-pound weight loss, drenching night sweats, shortness of breath, chest discomfort, and the sensation of his heart racing. He reported several "silver dollar"-sized lumps on his scalp and neck. He denied fevers, cough, orthopnea, and paroxysmal nocturnal dyspnea. The patient had a history of untreated human immunodeficiency virus (HIV), gastroesophageal reflux disease, an esophageal stricture that had been dilated 3 years prior, and a 30-pack-year smoking history.On initial exam, he was afebrile. His blood pressure was 115/73 mm Hg, his heart rate was 151 beats per minute, respirations were 20 per minute, and his oxygen saturation was 96% on room air. He had no murmurs, rubs, or gallops, but his jugular venous pressure was moderately elevated. His lungs were clear to auscultation bilaterally. His abdomen was not distended and was soft but exquisitely tender to mild palpation diffusely. His skin was damp, and he had several 3-cm diameter raised, palpable, firm, nontender lesions over his right temple and at the base of his neck.An electrocardiogram showed atrial flutter with 2:1 block. Chest radiography was unremarkable. Except for an elevated lactate dehydrogenase of 971 U/L and a CD4 count of 207 thousand/µL, his laboratory values, including