PubMed Health⌕ Search

Biomedical subjects

M Safak

Publications and source records attributed to M Safak.

At least 19 recordsLinked to original sources
PubMed2001

Cell cycle regulation of NF-kappa b-binding activity in cells from human glioblastomas.

Glioblastoma multiforme is a highly malignant and anaplastic tumor of the central nervous system representing more than 50% of all malignant gliomas. The cell origin of this highly undifferentiated tumor remains obscure, although it is postulated that glioblastomas are developed from astrocytes. The rapid growth of the glioma and the state of its undifferentiation are attributed to the deregulation of several signal transduction pathways and cell cycle events. Recent studies showed diverse functions for the NF-kappa B/Rel family of inducible transcription factors including differentiation, apoptosis, oncogenesis, and cell cycle regulation. We sought to examine the level of NF-kappa B activity throughout the glioma's cell cycle. Results from band-shift studies indicated a biphasic NF-kappa B DNA-binding activity in the nuclei of cycling glioblastoma cells. We showed that NF-kappa B-binding activity maximizes in nuclear extracts at specific cell cycle stages including G0/G1, mid-late G1, and S phase. Results from Northern blotting studies revealed that the differential expression of the NF-kappa B subunits, p50 and p65, may not be responsible for cell cycle stage-specific association of NF-kappa B subunits with DNA. However, results from Western blotting analysis utilizing nuclear extracts from glioma cells throughout the cell cycle demonstrated that the nuclear accumulation of p50 and p65 perfectly correlates with their DNA-binding activity. These observations suggest that the nuclear translocation of the p50/p65 subunit of NF-kappa B in glioma cells is cell cycle stage-dependent and that is distinct from the differential mRNA expression of these genes during glioma cell cycling. The possible role of NF-kappa B in glioma cell formation and regulation of cellular genes by NF-kappa B in these tumor cells is discussed.

Active Transport, Cell Nucleus↗
PubMed2001

Physical and functional interaction between viral and cellular proteins modulate JCV gene transcription.

The lytic phase of JC virus (JCV) appears to be highly complex and remains elusive. A growing body of experimental evidence suggests that the regulation of JCV gene expression and replication requires, in addition to the presence of specific transcription factors, cooperativity between viral and cellular regulatory proteins. This cooperativity may be accomplished by physical interaction of the participant proteins on and/or off the viral DNA sequence. Here, we present evidence of specific physical and functional interaction between a cellular factor, YB-1, and the JCV early protein, T-antigen, and showed that both proteins play important roles in JCV gene transcription. Additionally, our data indicate that YB-1 also functionally interact with another viral protein, designated agnoprotein, which is expressed late during the course of infection, adding further complexity to the currently known picture on JCV gene regulation.

Antigens, Viral, Tumor↗
PubMed2001

Interaction of JC virus agno protein with T antigen modulates transcription and replication of the viral genome in glial cells.

In addition to encoding the structural and regulatory proteins, many viruses encode auxiliary proteins, some of which have been shown to play important roles in lytic and latent states of the viruses. The human neurotropic JC virus (JCV) genome encodes an auxiliary protein called Agno whose function remains unknown. Here, we investigated the functional role of JCV Agno protein on transcription and replication of the viral genome in glial cells. Results from transfection of human glial cells showed that Agno protein suppresses both T-antigen-mediated transcription of the viral late gene promoter and T-antigen-induced replication of viral DNA. Affinity chromatography and coimmunoprecipitation assays demonstrated that the Agno protein and T antigen physically interact with each other. Through the use of a series of deletion mutants, we demonstrated that the T-antigen-interacting region of Agno protein is localized to its amino-terminal half and the Agno-interacting domain of T antigen maps to its central portion. Furthermore, utilizing various Agno deletion mutants in functional studies, we confirmed the importance of the Agno-T antigen interaction in the observed down-modulation of T antigen function upon viral gene transcription and DNA replication by Agno protein. Taken together these data suggest that the Agno protein of JCV, which is produced late during the late phase of the lytic cycle, can physically and functionally interact with the viral early protein, T antigen, and downregulate viral gene expression and DNA replication. The importance of these observations in the lytic cycle of JCV is discussed.

Amino Acid Sequence↗
PubMed2000

Extraperitoneal laparoscopic bladder neck suspension using hernia mesh and tacker.

OBJECTIVES: To report our initial experience with extraperitoneal bladder neck suspension for female stress incontinence due to urethral hypermobility. METHODS: Between September 1996 and September 1999, 35 patients (mean age 49.5 years) underwent extraperitoneal bladder neck suspension at our institution. An extraperitoneal space was created by a trocar-mounted balloon device, and suspension was created using a 5-mm endoscopic hernia stapler and polypropylene mesh. RESULTS: The mean operative time was 39.5 minutes. In 2 patients, the bladder was inadvertently perforated during the bladder neck dissection. The perforation was repaired by laparoscopic suture ligation. The mean urethral catheterization and hospitalization time was 2.1 and 2.3 days, respectively. Urethral recatheterization because of temporary urinary retention was required in 11.4% of the patients. Symptoms of bladder instability were experienced by 13.5% of the patients in the early postoperative period. A total of 28 patients (80.0%) reported that they were totally dry after a mean of 23.2 months. CONCLUSIONS: Extraperitoneal bladder neck suspension using hernia mesh and a stapler seems to be an effective and safe procedure, with a shorter operative time, in selected patient groups.

Adult↗
PubMed2000

Renomedullary interstitial cell tumor.

Renomedullary interstitial cell tumor was first introduced by Lerman and co-workers. These lesions have been referred to as medullary fibromas. The ultrastructural studies showed that the spindle cells throughout the stroma have the features of medullary interstitial cells. These benign tumors with specific histology are rare since they are incidental findings at autopsies. We report here a case of renomedullary interstitial cell tumor in a 55-year-old woman.

Female↗
PubMed1999

A 23-bp sequence element from human neurotropic JC virus is responsive to NF-kappa B subunits.

The regulatory region of the human neurotropic JC virus (JCV) is composed of several cis-acting motifs that confer cell type specificity to viral gene transcription and enable the viral promoters to respond to extracellular stimuli. For example, the bidirectional 98-bp tandem repeat sequences, positioned between the JCV early and late genes, were shown to be responsible for basal and activated levels of viral gene transcription in central nervous system (CNS) cells. Additionally, the NF-kappaB site located approximately 75 bp from the repeats on the early side of the viral genome was also found to influence both levels of viral transcription. Recently, we isolated a novel JCV variant, JCV(Phila-1), from a clinical specimen that contains a 23-bp sequence element (23-bpse) within its promoter-enhancer region. Here we demonstrate that this element is responsive to an extracellular stimulatory factor, such as phorbol 12-myristate 13-acetate (PMA), and can augment the basal levels of the viral early and to a lesser degree late promoter activities in cells derived from the CNS. The 23-bpse, by associating with nuclear proteins present in uninduced cells, forms a 40-kDa DNA-protein complex. Although no direct correlation between transcriptional enhancement of the JCV promoter by PMA treatment and the level of the 40-kDa DNA-protein complex was observed, results from site-directed mutagenesis indicated that formation of this complex is critical for the transcriptional activation of the viral promoter by PMA. These observations suggested that transcriptional enhancement of the JCV promoter activity upon PMA treatment may be an indirect event and mediated by an intermediary factor(s). In this respect, we demonstrated that overexpression of the inducible NF-kappaB subunits, p50 and p65, enhanced transcriptional activity of the JCV promoter through the 23-bp region with no evidence for their direct association with the 23-bpse DNA. Of importance, the p50/p65-induced JCV promoter activity requires the nucleotide sequences within the 23-bpse that are critical for the assembly of the 40-kDa DNA-protein complex. Thus, it is likely that the NF-kappaB subunits, by recruiting the cellular factors such as those associated with the 40-kDa DNA-protein complex, influence the basal level of the viral gene transcription. The implications of these findings with respect to regulation of viral and cellular genomes by extracellular stimuli and NF-kappaB pathway are discussed.

Base Composition↗
PubMed1999

Physical and functional interaction between the Y-box binding protein YB-1 and human polyomavirus JC virus large T antigen.

Y-box binding protein YB-1 is a member of a family of DNA and RNA binding proteins which have been shown to affect gene expression at both the transcriptional and translational levels. We have previously shown that YB-1 modulates transcription from the promoters of the ubiquitous human polyomavirus JC virus (JCV). Here we investigate the physical and functional interplay between YB-1 and the viral regulatory protein large T antigen (T-antigen), using JCV as a model system. Results of mobility band shift assays demonstrated that the efficiency of binding of YB-1 to a 23-bp single-stranded viral target sequence was significantly increased when T-antigen was included in the binding reaction mixture. Affinity chromatography and coimmunoprecipitation assays demonstrated that YB-1 and T-antigen physically interact with each other. Additionally, results of transcription studies demonstrated that these two proteins interact functionally on the JCV early and late gene promoters. Whereas ectopic expression of YB-1 and T-antigen results in synergistic transactivation of the viral late promoter, YB-1 alleviates T-antigen-mediated transcriptional suppression of the viral early promoter activity. Furthermore, we have localized, through the use of a series of deletion mutants, the sequences of these proteins which are important for their interaction. The T-antigen-interacting region of YB-1 is located in the cold shock domain of YB-1 and its immediate flanking sequences, and the YB-1-interacting domain of T-antigen maps to the carboxy-terminal half of T-antigen. Results of transient transfection assays with various YB-1 mutants and T-antigen expression constructs confirm the specificity of the functional interaction between YB-1 and T-antigen. Taken together, these data demonstrate that the cellular factor YB-1 and the viral regulatory protein T-antigen interact both physically and functionally and that this interaction modulates transcription from the JCV promoters.

Animals↗
PubMed1999

Reciprocal interaction between two cellular proteins, Puralpha and YB-1, modulates transcriptional activity of JCVCY in glial cells.

Cross communication between regulatory proteins is an important event in the control of eukaryotic gene transcription. Here we have examined the structural and functional interaction between two cellular regulatory proteins, YB-1 and Puralpha, on the 23-bp sequence element derived from the enhancer-promoter of the human polyomavirus JCV. YB-1 and Puralpha are single-stranded DNA binding proteins which recognize C/T- and GC/GA-rich sequences, respectively. Results from band shift studies demonstrated that while both proteins interact directly with their DNA target sequences within the 23-bp motif, each protein can regulate the association of the other one with the DNA. Affinity chromatography and coimmunoprecipitation provide evidence for a direct interaction between Puralpha and YB-1 in the absence of the DNA sequence. Ectopic expression of YB-1 and Puralpha in glial cells synergistically stimulated viral promoter activity via the 23-bp sequence element. Results from mutational studies revealed that residues between amino acids 75 and 203 of YB-1 and between amino acids 85 and 215 of Puralpha are important for the interaction between these two proteins. Functional studies with glial cells indicated that the region within Puralpha which mediates its association with YB-1 and binding to the 23-bp sequence is important for the observed activation of the JCV promoter by the Puralpha and YB-1 proteins. The results of this study suggest that the cooperative interaction between YB-1 and Puralpha mediates the synergistic activation of the human polyomavirus JCV genome by these cellular proteins. The importance of these findings for cellular and viral genes which are regulated by Puralpha and YB-1 is discussed.

Binding Sites↗
PubMed1998

Interaction of the single-stranded DNA-binding protein Puralpha with the human polyomavirus JC virus early protein T-antigen.

Large T-antigen, the major regulatory protein encoded by polyomaviruses, including Simian Virus 40 (SV40) and JC virus (JCV), is a multifunctional phosphoprotein that is involved in many viral and cellular events. In addition to its integral role in viral replication and cellular transformation, T-antigen also regulates transcription of both viral and cellular genes. In particular, the viral late promoter has been used as a model for the analysis of T-antigen-mediated transcriptional activation. Earlier studies have demonstrated that the cellular protein Puralpha is able to attenuate the transcriptional activity of JCV T-antigen. We investigated the mechanism whereby Puralpha affects T-antigen function. Co-immunoprecipitation studies demonstrated that Puralpha and JCV T-antigen associate in vivo, and glutathione S-transferase affinity binding assays revealed that these two proteins interact in vitro. Moreover, we localized the sequences of Puralpha that are important for the interaction between Puralpha and JCV T-antigen. In addition, we demonstrated that Puralpha interacts with the SV40 T-antigen. Transient transfection studies demonstrated that Puralpha and JCV T-antigen interact functionally as well. More specifically, Puralpha and a deletion mutant that interacts with T-antigen attenuated T-antigen-mediated transcriptional activation. A Puralpha deletion mutant that is unable to interact with JCV T-antigen, however, was found to be incapable of abrogating JCV T-antigen transactivation. Taken together, these data demonstrate that Puralpha and T-antigen interact both physically and functionally and that this interaction modulates T-antigen-mediated transcriptional activation. The implication of these findings with respect to the cellular role of Puralpha is discussed.

Antigens, Polyomavirus Transforming↗
PubMed1998

Long-term outcome of a patient with intrascrotal extratesticular malignant schwannoma.

We have the opportunity to present a rare case of late local recurrence after treatment of intrascrotal extratesticular malignant schwannoma with rhabdomyoblastic features in an adult man. As our case is the first in the literature, we want to inform the reader about the long-term follow-up of our patient and suggest that these tumors may have a long survival and late recurrences may occur even after 5 years postoperatively.

Chemotherapy, Adjuvant↗
PubMed1996

Transcription of the JC virus archetype late genome: importance of the kappa B and the 23-base-pair motifs in late promoter activity in glial cells.

The transcription control region of the archetype strain of the human polyomavirus JC virus (JCV(Cy)), unlike its neurotropic counterpart (JCV(Mad-1)), contains only one copy of the 98-bp enhancer/promoter repeat with the 23-bp and the 66-bp insertion blocks. Early studies by us and others have indicated that the structural organization of JCV(Mad-1) is critical for glial cell-specific transcription of the viral genome. In addition, the kappa B regulatory motif found in the JCV(Mad-1) genome, which also exists in JCV(Cy), confers inducibility to the JCV(Mad-1) early and late promoters in response to extracellular stimuli. In this study, we have investigated the regulatory role of the 23- and the 66-bp blocks and their functional relationship to the kappa B motif in stimulating transcription of the Cy early and late promoters in glial cells. We demonstrate that mutations in the kappa B motif reduce the basal activity of the Cy early promoter and decrease the levels of its induction by phorbol myristate acetate or factors derived from activated T cells. Under similar circumstances, mutation in the kappa B motif completely abrogated the basal and the induced levels of transcription of the viral late promoter. Using deletion and hybrid promoter constructs, we have demonstrated that the 23-bp block of the Cy promoter plays a critical role in the observed inactivation of Cy late promoter transcription in glial cells. Results from DNA binding studies have indicated the formation of a common nucleoprotein complex with the 23-bp sequence, mutant kappa B (kappa B(mut)), and wild-type kappa B (kappa B(wt)). Analysis of this complex by UV cross-linking has identified a 40-kDa protein which binds to the 23-bp sequence and the kappa B motif. The importance of these findings for the activation of JCV(Cy) under various physiological conditions is discussed.

Animals↗
PubMed1996

Transcriptional regulation of human polyomavirus JC: evidence for a functional interaction between RelA (p65) and the Y-box-binding protein, YB-1.

The transcriptional control region of the human neurotropic polyomavirus JC virus contains a consensus NF-kappa B site which has been shown to enhance both basal and extracellular stimulus-induced levels of transcription of JC promoters. Here, we show that the expression of JC late promoter constructs containing the NF-kappa B site is decreased by cotransfection with the NF-kappa B/rel subunits, p50 and p52, but enhanced by the p65 subunit. However, JC promoter constructs lacking the NF-kappa B site were activated by p52 and p50 and repressed by p65. This antithetical response of the JC promoter mapped specifically to the D domain, which is a target site for the cellular transcription factor, YB-1. Band shift studies indicated that YB-1 and p65 modulate each other's binding to DNA: YB-1 augments the affinity of p65 for the NF-kappa B site, while p65 reduces the binding of YB-1 to the D domain. Results from coimmunoprecipitation followed by Western blot (immunoblot) analysis suggest an in vivo interaction between p65 and YB-1 in glial cells. Functionally, YB-1 appears to act synergistically with p65 to control transcription from the NF-kappa B site. A converse pattern is seen with the D domain, in which YB-1 acts synergistically with p50 and p52 to regulate transcription. p50 and p52 may function as transcriptional activators on the D domain by removing the repressive effect of p65 on YB-1 binding to the D domain. On the basis of these data, we propose a model in which NF-kappa B/rel subunits functionally interact with consensus NF-kappa B sites or YB-1-binding sites, with disparate effects on eukaryotic gene expression.

Base Sequence↗
PubMed1996

Clinical experience with inflatable and malleable penile implants in 104 patients.

Penile prosthesis was implanted for erectile impotence of mainly organic origin in 104 patients. The AMS Dynaflex penile prosthesis was inserted in 39 cases, the AMS Malleable 600 prosthesis in 61 and the AMS Ultrex Plus prosthesis in 4. In 1 patient receiving a malleable prosthesis both rods had to be removed owing to erosion into the urethra and reimplantation was performed at the same operation. Only 1 patient who underwent implantation of the Dynaflex device had mechanical failure that necessitated surgical revision. After implantation of the new prosthesis both patients had satisfactory intercourse. One Dynaflex penile prosthesis, implanted into a juvenile-onset diabetic, became infected and required removal. Another complication was secondary to spontaneous erosion (noninfected) in 1 patient with malleable prosthesis who suffered loss of only one rod and who is still satisfied with the result. The overall complication rate in our series has been approximately 4%. The rest of the patients report satisfaction with the ability to move the penis voluntarily permitting normal sexual activities as well as normal appearance in the flaccid position. According to our experience, careful preoperative assessment from the views of both patient and device selection along with patient education, and strictly obeying the rules of sterility during implantation and applying systemic and local antimicrobial prophylaxis are essential in obtaining a successful result in prosthesis implantation for the individual patient.

Adult↗
PubMed1993

Characterisation of renal masses with colour flow Doppler ultrasonography.

Colour flow Doppler ultrasonography (US) was used in 24 renal masses (12 benign, 12 malignant) to investigate the vascularity of the lesion and thus to characterise the mass. A colour flow Doppler US device (Toshiba 270 A) with a convex probe of 3.75 MHz was used. Colour flow and the peak-systolic Doppler shift frequency obtained from the renal mass were used to distinguish between benign and malignant lesions. Ten of 12 malignant lesions demonstrated colour flow together with Doppler signals greater than 2.5 kHz (mean 3.5 kHz). None of the 12 benign renal masses demonstrated colour flow or tumour signals. The majority of malignant lesions give rise to neovascularisation and so high frequency Doppler-shifted signals. Thus colour flow Doppler sonography is the most reliable means of differentiating benign from malignant renal masses.

Adult↗