Biomedical subjects

J Qin

Publications and source records attributed to J Qin.

At least 55 records · Page 3Linked to original sources

PubMed2001

Compression of echocardiographic scan line data using wavelet packet transform.

An efficient compression strategy is indispensable for digital echocardiography. Previous work has suggested improved results utilizing wavelet transforms in the compression of 2D echocardiographic images. Set partitioning in hierarchical trees (SPIHT) was modified to compress echocardiographic scanline data based on the wavelet packet transform. A compression ratio of at least 94:1 resulted in preserved image quality.

Algorithms↗

PubMed2000

Differential association of products of alternative transcripts of the candidate tumor suppressor ING1 with the mSin3/HDAC1 transcriptional corepressor complex.

The candidate tumor suppressor ING1 was identified in a genetic screen aimed at isolation of human genes whose expression is suppressed in cancer cells. It may function as a negative growth regulator in the p53 signal transduction pathway. However, its molecular mechanism is not clear. The ING1 locus encodes alternative transcripts of p47(ING1a), p33(ING1b), and p24(ING1c). Here we report differential association of protein products of ING1 with the mSin3 transcriptional corepressor complex. p33(ING1b) associates with Sin3, SAP30, HDAC1, RbAp48, and other proteins, to form large protein complexes, whereas p24(ING1c) does not. The ING1 immune complexes are active in deacetylating core histones in vitro, and p33(ING1b) is functionally associated with HDAC1-mediated transcriptional repression in transfected cells. Our data provide basis for a p33(ING1b)-specific molecular mechanism for the function of the ING1 locus.

3T3 Cells↗

PubMed2000

Stable histone deacetylase complexes distinguished by the presence of SANT domain proteins CoREST/kiaa0071 and Mta-L1.

Human histone deacetylases I (HDAC1) and II (HDAC2) are homologous proteins (84% identity) that catalyze release of acetyl groups from modified N-terminal lysines of core histones. Histone deacetylation is correlated with both transient and persistent states of transcriptional inactivity (i.e. silencing) in many eukaryotes. In this study, we analyzed complexes containing HDAC1 and HDAC2 to identify the proteins most stably associated with these deacetylases. Complex cI (9.5 S) contained transcriptional corepressor CoREST/kiaa0071 and a protein homologous to FAD-dependent oxidoreductases, kiaa0601. Complex cII (15 S) contained >/=15 proteins, including CHD3/4 (Mi-2), Mta-L1, RbAp48/46, and MBD3, characteristic of vertebrate nucleosome-remodeling complexes. Under native conditions, cI and cII may contain HDAC1, HDAC2 or both; these can be dissociated to cI and cII core complexes containing only HDAC1 or HDAC2. The (m)CpG-binding protein MBD2 was associated only with the HDAC1 cII core complex. A model is proposed in which HDAC1 core complexes can be targeted to methylated DNA via MBD2 with recruitment of HDAC2 occurring through formation of HDAC1/2 cII dimers. We note that the cI component CoREST/kiaa0071 and the cII component Mta-L1 share a region of homology that includes a SANT domain; this domain may play a role in complex assembly.

Amino Acid Sequence↗

PubMed2000

Solution structure of the focal adhesion adaptor PINCH LIM1 domain and characterization of its interaction with the integrin-linked kinase ankyrin repeat domain.

PINCH is a recently identified adaptor protein that comprises an array of five LIM domains. PINCH functions through LIM-mediated protein-protein interactions that are involved in cell adhesion, growth, and differentiation. The LIM1 domain of PINCH interacts with integrin-linked kinase (ILK), thereby mediating focal adhesions via a specific integrin/ILK signaling pathway. We have solved the NMR structure of the PINCH LIM1 domain and characterized its binding to ILK. LIM1 contains two contiguous zinc fingers of the CCHC and CCCH types and adopts a global fold similar to that of functionally distinct LIM domains from cysteine-rich protein and cysteine-rich intestinal protein families with CCHC and CCCC zinc finger types. Gel-filtration and NMR experiments demonstrated a 1:1 complex between PINCH LIM1 and the ankyrin repeat domain of ILK. A chemical shift mapping experiment identified regions in PINCH LIM1 that are important for interaction with ILK. Comparison of surface features between PINCH LIM1 and other functionally different LIM domains indicated that the LIM motif might have a highly variable mode in recognizing various target proteins.

Amino Acid Sequence↗

PubMed2000

A dynamically tuned double-stranded RNA binding mechanism for the activation of antiviral kinase PKR.

A key step in the activation of interferon-inducible antiviral kinase PKR involves differential binding of viral double-stranded RNA (dsRNA) to its two structurally similar N-terminal dsRNA binding motifs, dsRBM1 and dsRBM2. We show here, using NMR spectroscopy, that dsRBM1 with higher RNA binding activity exhibits significant motional flexibility on a millisecond timescale as compared with dsRBM2 with lower RNA binding activity. We further show that dsRBM2, but not dsRBM1, specifically interacts with the C-terminal kinase domain. These results suggest a dynamically tuned dsRNA binding mechanism for PKR activation, where motionally more flexible dsRBM1 anchors to dsRNA, thereby inducing a cooperative RNA binding for dsRBM2 to expose the kinase domain.

Amino Acid Sequence↗

PubMed2000

High-dose chemoradiotherapy and autologous stem cell transplantation for patients with primary refractory aggressive non-Hodgkin lymphoma: an intention-to-treat analysis.

High-dose chemoradiotherapy (HDT) with autologous stem cell transplantation (ASCT) is the treatment of choice for patients with relapsed aggressive non-Hodgkin lymphoma (NHL). However, its role in the treatment of patients with primary refractory disease is not well defined. The outcomes of 85 patients with primary refractory aggressive NHL who underwent second-line chemotherapy with ICE with the intent of administering HDT/ASCT to those patients with chemosensitive disease were reviewed. Patients were retrospectively classified as induction partial responders (IPR) if they attained a partial response to doxorubicin-based front-line therapy or as induction failures (IF) if they had less than partial response. Forty-three patients (50.6%) had ICE-chemosensitive disease; there was no difference in the response rate between the IPR and the IF groups. Intention-to-treat analysis revealed that 25% of the patients were alive and 21.9% were event-free at a median follow-up of 35 months. Among 42 patients who underwent transplantation, the 3-year overall and event-free survival rates were 52.5% and 44.2%, respectively, similar to the outcomes for patients with chemosensitive relapsed disease. No differences were observed between the IPR and IF groups, and there were no transplantation-related deaths. More than one extranodal site of disease and a second-line age-adjusted International Prognostic Index of 3 or 4 before ICE chemotherapy were predictive of poor survival. These results suggest that patients with primary refractory aggressive NHL should receive second-line chemotherapy, with the intent of administering HDT/ASCT to those with chemosensitive disease. Newer therapies are needed to improve the outcomes of patients with poor-risk primary refractory disease.

Adult↗

PubMed2000

Cell cycle-regulated phosphorylation of p220(NPAT) by cyclin E/Cdk2 in Cajal bodies promotes histone gene transcription.

Cyclin E/Cdk2 acts at the G1/S-phase transition to promote the E2F transcriptional program and the initiation of DNA synthesis. To explore further how cyclin E/Cdk2 controls S-phase events, we examined the subcellular localization of the cyclin E/Cdk2 interacting protein p220(NPAT) and its regulation by phosphorylation. p220 is localized to discrete nuclear foci. Diploid fibroblasts in Go and G1 contain two p220 foci, whereas S- and G2-phase cells contain primarily four p220 foci. Cells in metaphase and telophase have no detectable focus. p220 foci contain cyclin E and are coincident with Cajal bodies (CBs), subnuclear organelles that associate with histone gene clusters on chromosomes 1 and 6. Interestingly, p220 foci associate with chromosome 6 throughout the cell cycle and with chromosome 1 during S phase. Five cyclin E/Cdk2 phosphorylation sites in p220 were identified. Phospho-specific antibodies against two of these sites react with p220 within CBs in a cell cycle-specific manner. The timing of p220 phosphorylation correlates with the appearance of cyclin E in CBs at the G1/S boundary, and this phosphorylation is maintained until prophase. Expression of p220 activates transcription of the histone H2B promoter. Importantly, mutation of Cdk2 phosphorylation sites to alanine abrogates the ability of p220 to activate the histone H2B promoter. Collectively, these results strongly suggest that p220(NPAT) links cyclical cyclin E/Cdk2 kinase activity to replication-dependent histone gene transcription.

Amino Acid Sequence↗

PubMed2000

Involvement of the TIP60 histone acetylase complex in DNA repair and apoptosis.

It is well known that histone acetylases are important chromatin modifiers and that they play a central role in chromatin transcription. Here, we present evidence for novel roles of histone acetylases. The TIP60 histone acetylase purifies as a multimeric protein complex. Besides histone acetylase activity on chromatin, the TIP60 complex possesses ATPase, DNA helicase, and structural DNA binding activities. Ectopic expression of mutated TIP60 lacking histone acetylase activity results in cells with defective double-strand DNA break repair. Importantly, the resulting cells lose their apoptotic competence, suggesting a defect in the cells' ability to signal the existence of DNA damage to the apoptotic machinery. These results indicate that the histone acetylase TIP60-containing complex plays a role in DNA repair and apoptosis.

Acetyltransferases↗

PubMed2000

Both corepressor proteins SMRT and N-CoR exist in large protein complexes containing HDAC3.

We present evidence that both corepressors SMRT and N-CoR exist in large protein complexes with estimated sizes of 1.5-2 MDa in HeLa nuclear extracts. Using a combination of conventional and immunoaffinity chromatography, we have successfully isolated a SMRT complex and identified histone deacetylase 3 (HDAC3) and transducin (beta)-like I (TBL1), a WD-40 repeat-containing protein, as the subunits of the purified SMRT complex. We show that the HDAC3-containing SMRT and N-CoR complexes can bind to unliganded thyroid hormone receptors (TRs) in vitro. We demonstrate further that in Xenopus oocytes, both SMRT and N-CoR also associate with HDAC3 in large protein complexes and that injection of antibodies against HDAC3 or SMRT/N-CoR led to a partial relief of repression by unliganded TR/RXR. These findings thus establish both SMRT and N-CoR complexes as bona fide HDAC-containing complexes and shed new light on the molecular pathways by which N-CoR and SMRT function in transcriptional repression.

Animals↗

PubMed2000

Immunohistochemical expression of doublecortin in the human cerebrum: comparison of normal development and neuronal migration disorders.

Immunohistochemical expression of the doublecortin (DCX) gene product was investigated in cerebral cortices from 33 normal developing human, aged 9 gestational weeks (GW) to 29 years, and from 26 patients with various neuronal migration disorders, aged 19 GW to 34 years. DCX immunoreactivity was detected predominantly in the fetal cerebral cortex. The neurons in the cortical plate (CP) exhibited positive labeling at 9 GW. Staining was the most marked intense at 12-20 GW, and gradually decreased thereafter, only relatively weak immunoreactivity remaining in pyramidal cells. Comparison of the immunohistochemical characteristics of DCX and those of nestin and vimentin indicated the early expression of DCX in neuroepithelial stem cells of the subventricular germinal layer, as well as in neurons of the CP. The most marked intense expression in the period of neuronal migration strongly indicated its role in neuronal migration. The abnormal distribution of DCX immunolabeling in the cerebral cortex was associated with a neuronal disarrangement in some migration disorders, such as Miller-Dieker syndrome and Fukuyama congenital muscular dystrophy. Decreased DCX immunolabeling was demonstrated in fetuses and infants with Zellweger syndrome, implicating DCX in the neuronal migration abnormality in this syndrome.

Adolescent↗

PubMed2000

BASC, a super complex of BRCA1-associated proteins involved in the recognition and repair of aberrant DNA structures.

We report the identities of the members of a group of proteins that associate with BRCA1 to form a large complex that we have named BASC (BRCA1-associated genome surveillance complex). This complex includes tumor suppressors and DNA damage repair proteins MSH2, MSH6, MLH1, ATM, BLM, and the RAD50-MRE11-NBS1 protein complex. In addition, DNA replication factor C (RFC), a protein complex that facilitates the loading of PCNA onto DNA, is also part of BASC. We find that BRCA1, the BLM helicase, and the RAD50-MRE11-NBS1 complex colocalize to large nuclear foci that contain PCNA when cells are treated with agents that interfere with DNA synthesis. The association of BRCA1 with MSH2 and MSH6, which are required for transcription-coupled repair, provides a possible explanation for the role of BRCA1 in this pathway. Strikingly, all members of this complex have roles in recognition of abnormal DNA structures or damaged DNA, suggesting that BASC may serve as a sensor for DNA damage. Several of these proteins also have roles in DNA replication-associated repair. Collectively, these results suggest that BRCA1 may function as a coordinator of multiple activities required for maintenance of genomic integrity during the process of DNA replication and point to a central role for BRCA1 in DNA repair.

Adenosine Triphosphatases↗

PubMed2000

A structural basis for integrin activation by the cytoplasmic tail of the alpha IIb-subunit.

A key step in the activation of heterodimeric integrin adhesion receptors is the transmission of an agonist-induced cellular signal from the short alpha- and/or beta-cytoplasmic tails to the extracellular domains of the receptor. The structural details of how the cytoplasmic tails mediate such an inside-out signaling process remain unclear. We report herein the NMR structures of a membrane-anchored cytoplasmic tail of the alpha(IIb)-subunit and of a mutant alpha(IIb)-cytoplasmic tail that renders platelet integrin alpha(IIb)beta(3) constitutively active. The structure of the wild-type alpha(IIb)-cytoplasmic tail reveals a "closed" conformation where the highly conserved N-terminal membrane-proximal region forms an alpha-helix followed by a turn, and the acidic C-terminal loop interacts with the N-terminal helix. The structure of the active mutant is significantly different, having an "open" conformation where the interactions between the N-terminal helix and C-terminal region are abolished. Consistent with these structural differences, the two peptides differ in function: the wild-type peptide suppressed alpha(IIb)beta(3) activation, whereas the mutant peptide did not. These results provide an atomic explanation for extensive biochemical/mutational data and support a conformation-based "on/off switch" model for integrin activation.

Amino Acid Sequence↗

PubMed2000

Vitamin A equivalence of beta-carotene in a woman as determined by a stable isotope reference method.

BACKGROUND: Quantitative information on conversion of beta-carotene to vitamin A in humans is limited. AIM OF THE STUDY: Our laboratory has developed a stable isotope method for studying the conversion of beta-carotene (beta-C) to vitamin A. METHODS: Two dosage levels (a pharmacological dose, 126.0 mg beta-C-d8, and a physiological dose, 6.0 mg beta-C-d8) were used 2.5 y apart in an adult female volunteer to study dose effects on the conversion of beta-C to vitamin A. Blood samples were collected over 21 d. beta-C and retinol were extracted from serum and isolated by high performance liquid chromatography. The retinol fraction was derivatized to a trimethylsilyl ether which was analyzed by gas chromatograph/mass spectrometry with electron capture negative chemical ionization. RESULTS: The retinol-d4 response in the circulation peaked at 24 hours after the beta-C-d8 dose, with a higher percent enrichment after the pharmacological dose than after the physiological dose. By using retinyl acetate-d8 as the vitamin A reference, the retinol-d4 formed from 6 mg of beta-C-d8 (11.2 mumol) was calculated to be equivalent to 1.6 mg of retinol (i.e., 3.8 mg of beta-C was equivalent to 1 mg of retinol). However, the retinol-d4 formed from 126 mg of beta-C-d8 (235 mumol) was equivalent to 2.3 mg of retinol (i.e., 55 mg beta-C was equivalent to 1 mg retinol). CONCLUSION: These results provide evidence that it is feasible to use stable isotope reference method to study retinol equivalence of beta-C and that there may be a dose-dependence on bioconversion of beta-carotene to retinol.

Adult↗

PubMed2000

A novel migration-related gene product, doublecortin, in neuronal migration disorder of fetuses and infants with Zellweger syndrome.

Immunohistochemical expression of doublecortin (DCX), KIAA0369 (KIA) and LIS1 proteins as well as nestin and vimentin in the cerebral cortices of six patients with Zellweger syndrome (ZS), aged 19 gestational weeks (GW) to 8 months, was compared with that in nine controls, aged 12 GW to 8 months. DCX immunoreactivity was apparently reduced in ZS, particularly in the cortical plate of fetuses, and in the subependymal foci of heterotopic neurons of the infants. Reduced expression of DCX in ZS was confirmed by Western blot analysis. On the other hand, neuronal expression of nestin was high in the cortical plate, migrating cells of the white matter and germinal cells in the ventricular zone in fetuses with ZS. Immunoreactivities for KIA, LIS1 and vimentin in ZS were comparable to those of controls. Reduced expression of DCX may be responsible for the neuronal migration disorder, and increased expression of nestin may be another evidence for delayed neuronal maturation in ZS.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed2000

Intraoperative echocardiographic detection of regurgitant jets after valve replacement.

BACKGROUND: Paravalvular jets, documented by intraoperative transesophageal echocardiography, have prompted immediate valve explantation by others, yet the significance of these jets is unknown. METHODS: Twenty-seven patients had intraoperative transesophageal two-dimensional color Doppler echocardiography, performed to assess the number and area of regurgitant jets after valve replacement, before and after protamine. Patients were grouped by first time versus redo operation, valve position and type. RESULTS: Before protamine, 55 jets were identified (2.04+/-1.4 per patient) versus 29 jets after (1.07+/-1.2 per patient, p = 0.0002). Total jet area improved from 2.0+/-2.2 cm2 to 0.86+/-1.7 cm2 with protamine (p<0.0001). In all patients jet area decreased (average decrease, 70.7%+/-27.0%). First time and redo operations had similar improvements in jet number and area (both p>0.6). Furthermore, mitral and mechanical valves each had more jets and overall greater jet area when compared to aortic and tissue valves, respectively. CONCLUSIONS: Following valve replacement, multiple jets are detected by intraoperative transesophageal echocardiography. They are more common and larger in the mitral position and with mechanical valves. Improvement occurs with reversal of anticoagulation.

Adult↗

PubMed2000

Cosgrove-Edwards Annuloplasty System: midterm results.

BACKGROUND: The Cosgrove-Edwards Annuloplasty System includes a universally flexible band that corrects mitral annular dilatation via measured plication of the posterior annulus. The purpose of this study was to evaluate midterm clinical and functional results in the first 197 patients receiving this flexible annuloplasty band at mitral valve repair. METHODS: From February 1993 to July 1994, 197 consecutive patients with mitral regurgitation had mitral valve repair using this system. Valve disease was degenerative in 73%, rheumatic in 15%, ischemic in 5%, infectious in 2.5%, and other in 4%. RESULTS: Immediately after repair, echocardiographic mitral regurgitation was none or trivial in 92%, 1+ in 5%, and 2+ in 3%. There were no hospital deaths. Late follow-up was available in 195 patients (99%), with 661 patient-years of follow-up available for analysis. Four-year actuarial survival was 93%, freedom from thromboembolism 94%, from endocarditis 98%, and from reoperation 95%. At a mean interval of 18 months, echocardiography in 157 patients demonstrated no or trace mitral regurgitation in 56%, 1+ in 24%, 2+ in 9%, 3+ in 6%, and 4+ in 3%. At a mean of 61 +/- 5 months, reconstruction of the mitral annulus from real-time three-dimensional echocardiographic images in 10 patients confirmed preserved nonplanar shape and sphincter mechanism of the mitral annulus. Annular orifice area decreased 28% +/- 11% during the cardiac cycle from a mean of 10.1 +/- 3.9 cm2 in diastole to 7.2 +/- 2.8 cm2 in systole. CONCLUSIONS: This annuloplasty system is effective for repair of mitral regurgitation secondary to all causes and preserves mitral annular flexibility and function at 5-year follow-up.

Female↗

PubMed2000

Concerted dephosphorylation of the transcription factor NFAT1 induces a conformational switch that regulates transcriptional activity.

NFAT transcription factors are highly phosphorylated proteins that are regulated by the calcium-dependent phosphatase calcineurin. We show by mass spectrometry that NFAT1 is phosphorylated on fourteen conserved phosphoserine residues in its regulatory domain, thirteen of which are dephosphorylated upon stimulation. Dephosphorylation of all thirteen residues is required to mask a nuclear export signal (NES), cause full exposure of a nuclear localization signal (NLS), and promote transcriptional activity. An inducible phosphorylation site in the transactivation domain contributes to transcriptional activity. Our data suggest that dephosphorylation promotes NFAT1 activation by increasing the probability of an active conformation, in a manner analogous to that by which depolarization increases the open probability of voltage-gated ion channels. This conformational switch paradigm may explain modification-induced functional changes in other heavily phosphorylated proteins.

Animals↗

PubMed2000

The USA-derived transcriptional coactivator PC2 is a submodule of TRAP/SMCC and acts synergistically with other PCs.

PC2, the high-molecular weight constituent of the potent USA transcriptional coactivator fraction, was identified as a Mediator-like complex. Its composition resembles that of the TRAP/SMCC complex, but PC2 is distinguished by the prominent absence of the SRB10 and SRB11 kinase/cyclin pair, as well as several additional polypeptides. Furthermore, affinity-purified PC2, which lacks independent activity, acts in synergy with USA-derived coactivators PC3/topoisomerase I and PC4 to mediate the effects of a variety of activators (including VP16, the synthetic activator GAL4-AH, and the orphan nuclear receptor HNF4) and thus recapitulates partial USA coactivator function.

HeLa Cells↗