Eun A. Kim

Phosphorylation by the DHIPK2 Protein Kinase Modulates the Corepressor Activity of Groucho

Groucho function is essential for Drosophila development, acting as a corepressor for specific transcription factors that are downstream targets of various signaling pathways. Here we provide evidence that Groucho is phosphorylated by the DHIPK2 protein kinase. Phosphorylation modulates Groucho corepressor activity by attenuating its protein-protein interaction with a DNA-bound transcription factor. During eye development, DHIPK2 modifies Groucho activity, and eye phenotypes generated by overexpression of Groucho differ depending on its phosphorylation state. Moreover, analysis of nuclear extracts fractionated by column chromatography further shows that phospho-Groucho associates poorly with the corepressor complex, whereas the unphosphorylated form binds tightly. We propose that Groucho phosphorylation by DHIPK2 and its subsequent dissociation from the corepressor complex play a key role in relieving the transcriptional repression of target genes regulated by Groucho, thereby controlling cell fate determination during development.

Phosphorylation and Transactivation of Pax6 by Homeodomain-interacting Protein Kinase 2

Pax6 is a transcriptional activator that contains two DNA binding domains and a potent transcription activation domain in the C terminus, which regulates organogenesis of the eye, nose, pancreas, and central nervous system. Homeodomain-interacting protein kinase 2 (HIPK2) interacts with transcription factors, including homeoproteins, and regulates activities of transcription factors. Here we show that HIPK2 phosphorylates the activation domain of Pax6, which augments Pax6 transactivation by enhancing its interaction with p300. Mass spectrometric analysis identified three Pax6 phosphorylation sites as threonines 281, 304, and 373. The substitutions of these threonines with alanines decreased Pax6 transactivation, whereas substitutions to glutamic acids increased transactivation in mimicry of phosphorylation. Furthermore, the knock-down of either endogenous or exogenous HIPK2 expression with HIPK2 shRNA markedly inhibited Pax6 phosphorylation and its transactivating function on proglucagon promoter in cultured cells. These results strongly indicate that HIPK2 is an upstream protein kinase for Pax6 and suggest that it modulates Pax6-mediated transcriptional regulation.

Small Pulmonary Nodules on Ct Accompanying Surgically Resectable Lung Cancer: Likelihood of Malignancy

The aim of this study was to determine the likelihood of malignancy in small nodules in the nonprimary lobe in patients with resectable bronchogenic carcinoma. In 141 patients who underwent curative resection of bronchogenic carcinoma and had adequate follow-up CT examinations, the presence of small nodules in the nonprimary lobe preoperatively and change of preexisting nodules, if any, was assessed. The criteria used to determine benignity of a nodule was stability or decrease in size for 24 months on CT. Histopathology of the nodules was reviewed for an additional 10 patients who underwent surgical biopsy for an accompanying nodule before curative surgery. Sixty-two (44%) of 141 patients had a total of 138 small (≤ 10 mm) nodules in the nonprimary lobes (< 5 mm in 113, 5–10 mm in 25). Of these 138 nodules, 132 were benign with only six nodules malignant (with histopathologic confirmation for the enlarging nodules). The 132 benign nodules showed no change (n = 120), decrease in size (n = 11), or increase in size (n = 1) on follow-up studies, with the single enlarging nodule proved benign on biopsy. In 10 patients who had a preoperative biopsy of a single preexisting nodule in the nonprimary lobe (< 5 mm = 1; 5–10 mm = 5; > 10 mm = 4) two proved to be malignant (both > 10 mm) and eight were benign. Most small (< 10 mm) nodules associated with resectable bronchogenic carcinoma are benign, consistent with published results of other studies. However, a small number of nodules are malignant and CT does not reliably distinguish between benign and malignant nodules.

Interstitial pneumonia in progressive systemic sclerosis: serial high-resolution CT findings with functional correlation.

Purpose The aim of our study was to assess the serial high-resolution CT findings and their correlation with the results of pulmonary function tests in patients with progressive systemic sclerosis (PSS) and interstitial pneumonia. Method The study included 40 patients with symptoms or signs of PSS and interstitial pneumonia, who underwent serial high-resolution CT scans (mean follow-up period 39 months). Seventeen patients simultaneously had serial pulmonary function tests (mean follow-up period 40 months). On high-resolution CT, the pattern and extent of parenchymal abnormalities were retrospectively analyzed. Serial changes on high-resolution CT were correlated with the changes of pulmonary function tests. Results On initial CT, areas of ground-glass opacity (mean ± SD extent 17.7 ± 12.3% in all patients), irregular linear opacity (4.4 ± 4.4% in 36 patients), small nodules (3.9 ± 12.5% in 28), consolidation (1.9 ± 4.2% in 13), and honeycombing (1.9 ± 3.8% in 12) were seen. The total disease extent (p = 0.042) and extents of ground-glass opacity (18.9 ± 15.5%; p = 0.04) and honeycombing (5.0 ± 7.2%; p = 0.002) increased significantly on follow-up CT. Both forced vital capacity (from 2.4 ± 0.4 to 2.0 ± 0.4 L; p = 0.002) and forced expiratory volume in 1 s (from 2.0 ± 0.4 to 1.6 ± 0.3 L; p = 0.013) decreased significantly on follow-up examination. The increase in the extent of honeycombing on CT correlated significantly with the decrease in diffusing capacity for carbon monoxide (r = −0.411, p = 0.049). Conclusion In patients with PSS and interstitial pneumonia, the overall extent of disease and extents of honeycombing and ground-glass opacity increase significantly on follow-up CT. Increase of honeycombing correlates well with decrease of diffusing capacity for carbon monoxide.