PubMed Health⌕ Search

Biomedical subjects

C Mark

Publications and source records attributed to C Mark.

At least 19 recordsLinked to original sources
PubMed2001

Conserved interaction between distinct Krüppel-associated box domains and the transcriptional intermediary factor 1 beta.

The Krüppel-associated box (KRAB) domain, originally identified as a 75-aa sequence present in numerous Krüppel-type zinc-finger proteins, is a potent DNA-binding-dependent transcriptional repression domain that is believed to function through interaction with the transcriptional intermediary factor 1 (TIF1) beta. On the basis of sequence comparison and phylogenetic analysis, we have recently defined three distinct subfamilies of KRAB domains. In the present study, individual members of each subfamily were tested for transcriptional repression and interaction with TIF1 beta and two other closely related family members (TIF1 alpha and TIF1 gamma). All KRAB variants were shown, (i) to repress transcription when targeted to DNA through fusion to a heterologous DNA-binding domain in mammalian cells, and (ii) to interact specifically with TIF1 beta, but not with TIF1 alpha or TIF1 gamma. Taken together, these results implicate TIF1 beta as a common transcriptional corepressor for the three distinct subfamilies of KRAB zinc-finger proteins and suggest a high degree of conservation in the molecular mechanism underlying their transcriptional repression activity.

Animals↗
PubMed2001

Molecular cloning and preliminary functional analysis of two novel human KRAB zinc finger proteins, HKr18 and HKr19.

cDNA clones encoding two novel human KRAB zinc finger proteins, HKr18 and HKr19, were isolated from a human testis cDNA library. Their corresponding genes were later identified in sequences originating from chromosomes 19 and 7, respectively. On the basis of the collected information from gene and cDNA sequences, Hkr18 was found to be a protein of 94 kDa with 20 zinc finger motifs in its C terminus. The HKr19 is a smaller protein, with a molecular weight of 56 kDa containing 11 zinc finger motifs. Both HKr18 and HKr19 contained a KRAB A as well as a KRAB B domain in their N termini. Northern blot analysis showed expression of HKr18 in all human tissues tested, indicating a ubiquitous expression pattern. In contrast, HKr19 showed a more restricted tissue distribution, with detectable expression primarily in testis and fetal tissues. The HKr19 protein is a member of the large ZNF91 subfamily of KRAB zinc finger genes. A PCR-based analysis of the expression of HKr19 and other closely related genes showed that lymphoid, myeloid, and nonhematopoietic cells expressed different sets of these genes. This latter finding indicates that some members of the ZNF91 family may be involved in regulating lineage commitment during hematopoietic development. Transfection of various parts of HKr19 into human embryonic kidney cells (HEK 293 cells) showed that the entire protein and its zinc finger region were toxic to these cells when expressed at high levels. In contrast, the KRAB domain and the linker region seemed to be well tolerated.

Adult↗
PubMed1999

Comparative analysis of KRAB zinc finger proteins in rodents and man: evidence for several evolutionarily distinct subfamilies of KRAB zinc finger genes.

Although the KRAB zinc finger proteins probably constitute the single largest class of transcription factors within the human genome, almost nothing is known about their biological function. To increase our knowledge about this interesting and relatively unexplored family of potent transcriptional repressors, we here present the cloning, structural analysis, and expression study of three novel mouse KRAB zinc finger proteins. In addition, we present an extensive comparative analysis of various members of this gene family based on the structure of the common KRAB A motif. At least three larger subfamilies of KRAB zinc finger proteins are identified: one carrying the classical KRAB A motif only, another holding both a classical KRAB A and a classical KRAB B motif, and a third holding a classical KRAB A and a highly divergent KRAB B domain, named b. A large variation both in size and in primary amino acid sequence was observed in the linker region between the KRAB domain and the C-terminally located zinc finger repeats. This variability indicates that this region is of minor importance for the biological function of KRAB-containing zinc finger proteins. The fact that in many zinc finger genes, the entire or almost the entire linker region is composed of degenerate finger motifs substantiates this conclusion. The absence of identifiable KRAB A and B motifs in the genome of yeast, Saccharomyces cerevisiae, indicates a relatively late appearance of the KRAB domain in evolution and may suggest that the biological functions are restricted to multicellular organisms. In addition, we show that the expression of individual members of one subfamily of KRAB zinc finger genes is restricted to specific hematopoietic cell lineages. This finding suggests that KRAB zinc finger proteins may play a role in lineage commitment, possibly silencing leakage transcription from nonlineage-expressed genes.

Amino Acid Sequence↗
PubMed1997

Functional epitope mapping of insulin-like growth factor I (IGF-I) by anti-IGF-I monoclonal antibodies.

Based on a collection of monoclonal antibodies (mAb) against insulin-like growth factor I (IGF-I), we have defined the IGF-I epitopes involved in the interaction with IGF-binding proteins (IGFBP) and IGF-I receptors. We have also characterized the ability of these antibodies to block IGF-I-induced survival of the IL-3-dependent Ba/F3 cell line. More than 140 hybridomas secreting IGF-I-specific mAb were characterized, of which 28 were studied in detail. They display apparent affinity constants ranging from less than 10(6) to 10(10) M-1 and varying crossreactivity with IGF-II, including 2 mAb with higher affinity for IGF-II than for IGF-I. None crossreact with insulin or any other growth factor tested. Using both enzyme immunoassays and real-time biospecific interaction analysis, we have identified 8 epitopic clusters related to the primary structure of IGF-I, according to mAb reactivity to synthetic peptides, proteolytic fragments of IGF-I, and various IGF-I mutants. The mAb panel also was used to map the IGF domains implicated in the interaction with IGFBP and IGF-I receptors. An IGF-I domain has been identified that remains exposed after IGF-I binding to IGFBP-1 or to IGFBP-3, which is recognized by 6 different mAb. The mAb in this group also bind IGF-I, when complexed to the type-1 IGF receptor on the murine pro-B cell line Ba/F3, and BALB/c 3T3 fibroblasts overexpressing the human receptor. Finally, IGF-I-promoted survival can be blocked with mAb specific for target epitopes, and their potential use in tumor cell growth control is discussed.

Animals↗
PubMed1991

Glucose challenge testing in pregnancy.

This study examines results of routine glucose challenge screening in 608 third-trimester patients in a private practice setting. Four patient categories were defined on the basis of the results: normal, abnormal screen with normal glucose tolerance test, borderline glucose tolerance test, and gestational diabetes. When only standard prenatal management practices were used, the fetal outcomes in the four groups were not measurably different. The costs of these procedures resulted in an expenditure of $722.31 per diagnosis of gestational diabetes. This seems excessive in view of the negligible impact of these studies on fetal outcome. Our impression was that routine third-trimester dietary counseling, postprandial glucose monitoring without challenge testing, and evaluation of cases of suspected fetal macrosomia would result in comparable outcome at significantly reduced cost.

Adult↗
PubMed1989

RBC lithium transport in the psychoses.

In vitro and in vivo red blood cell (RBC) lithium (Li+) intracellular/extracellular ratios were determined in 93 DSM-III schizophrenics (SCZ) in 47 DSM-III schizophreniform disorder patients (SF), in 22 DSM-III bipolar manics (M), in 15 affective disorders patients with mood-incongruent psychotic features (AD-MIP), and in 40 normal controls. There were no significant differences among groups in the in vitro Li+ ratio. Similarly, there was no significant difference among patient groups in the in vivo Li+ ratio. Furthermore, there was no significant difference in the mean Li+ ratios between the Li+-responsive and nonresponsive schizophrenic-like subjects. However, the distribution of Li+ ratios (both in vitro and in vivo) in the Li+-responsive group was significantly abnormal, showing more ratios in the extremes of the distribution (a platykurtic distribution).

Bipolar Disorder↗
PubMed1987

Complete or partial homozygosity of chromosome 13 in primary retinoblastoma.

Sixteen retinoblastomas were examined with chromosome 13 polymorphic probes to determine the frequency of homozygosity for the chromosome in the tumors. Each of the tumors had two cytogenetically normal appearing No. 13 chromosomes. Nontumorous cells from the same patients were heterozygous for the various polymorphic chromosome 13 probes used. At least partial homozygosity for a single chromosome 13 was observed in 75% of the tumors. These studies confirm and extend previous studies which suggest that homozygosity or hemizygosity at RBI occurs in the majority of retinoblastomas. We also demonstrate in an additional tumor that rapid clonal evolution from hemizygosity to homozygosity can occur in the tumor.

Cells, Cultured↗
PubMed1986

Preinduction cervical ripening with sequential use of prostaglandin E2 gel.

Two hundred patients received a prostaglandin E2-containing gel for preinduction cervical ripening. The gel was administered every 6 hours until a Bishop score greater than or equal to 7 was obtained or the attending physician deemed induction necessary. Forty-eight percent of the patients labored "spontaneously" after one or more gel applications. The average cumulative change in Bishop score with sequential application of the gel was 2.7. Sequential application of the prostaglandin gel proved no more effective in the process of preinduction cervical ripening than single application of the gel with a similar period of observation.

Cervix Uteri↗
PubMed1985

Characteristics of phospholipid methylation in human erythrocyte ghosts: relationship(s) to the psychoses and affective disorders.

Recent studies have shown that patients with a schizophrenic-like illness have a significant deficit in erythrocyte ghost membrane (EGM) phosphatidylcholine (PC); patients with the most severe deficiency showed a marked decrease in Na+-Li+ counterflow activity (Hitzemann et al. 1984a and b). The present study was undertaken to see if the decrement in PC is associated with a decrease in phospholipid methylation activity. Phospholipid methylation in human EGMs is distinctly different from that in rat EGMs (Hirata and Axelrod 1980) in that the human activity is not Mg++-dependent, and apparent methyltransferase I activity is located in the external membrane surface. The patient population consisted of 20 DSM-III schizophrenics (SCZ), 13 DSM-III schizophreniform (SF) disorder patients, and 11 DSM-III manics (M). Twelve age- and sex-matched controls were used for the comparison group. Methylation activity was significantly decreased in all three patient groups, although the M group had significantly higher activity than the SF group. Twenty-four of the SCZ and SF patients entered a Li+ trial. The Li+ responder group (n = 8) showed significantly lower activity than the nonresponder group (n = 16). Overall, we conclude that the decrement in phospholipid methylation activity partially contributes to the decrement in PC levels.

Adult↗
PubMed1984

Membranes, methylation and lithium responsive psychoses.

Data are presented showing that the erythrocyte ghost membranes of lithium-responsive and non-responsive schizophrenic-like patients are different from control membranes. In both groups of patients there was a significant decrement of phosphatidylcholine (PC) which was largely compensated for by an increase in sphingomyelin. The decrement in PC may in part be associated with a decrease in phospholipid methylation which converts phosphatidylethanolmine (PE) to PC. Interestingly, in the lithium-responsive but not the non-responsive patients, lithium stimulates methylation activity. This stimulation may affect a variety of membrane functions, e.g. adenyl cyclase activity, which would be involved in lithium's therapeutic actions.

Blood Platelets↗
PubMed1984

Tumorigenicity of human HT1080 fibrosarcoma X normal fibroblast hybrids: chromosome dosage dependency.

The tumorigenic capacity of hybrids formed by fusion of the highly tumorigenic HT1080 human fibrosarcoma cell line with nontumorigenic normal fibroblasts was examined. The HT1080 also contains an activated N-ras oncogene. Near-tetraploid hybrids which contained an approximately complete chromosomal complement from both parental cells were nontumorigenic when 1 X 10(7) cells were injected s.c. into athymic (nude) mice, whereas the parental HT1080 cells produced tumors in 100% of the animals with no latency period following injection of 2 X 10(6) cells. Tumorigenic variants were obtained from these hybrids which had lost only a few chromosomes compared to cells from the nontumorigenic mass cultures. In addition, several near-hexaploid hybrids were obtained which contained approximately a double chromosomal complement from the HT1080 parental line and a single chromosomal complement from the normal fibroblasts. All of these near-hexaploid hybrids produce tumors in 100% of nude mice with no latency period. Our results indicate that tumorigenicity of these particular human malignant cells of mesenchymal origin can be suppressed when fused with normal diploid fibroblasts. In addition, the results suggest that tumorigenicity in this system is chromosomal dosage dependent, since a diploid chromosomal complement from normal fibroblasts is capable of suppressing the tumorigenicity of a near-diploid but not a near-tetraploid chromosomal complement from the tumorigenic HT1080 parent. Finally, the loss of chromosome 1 (the chromosome to which the N-ras oncogene has been assigned) as well as chromosome 4 was correlated with the reappearance of tumorigenicity in the rare variant populations from otherwise nontumorigenic near-tetraploid hybrid cultures. Our results also suggest the possibility that tumorigenicity in these hybrids may be a gene dosage effect involving the number of activated N-ras genes in the hybrids compared to the gene(s) controlling the suppression of the activated N-ras genes.

Cell Fusion↗
PubMed1983

A comparison of prostaglandin E2 gel and prostaglandin F2 alpha gel for preinduction cervical ripening.

The unfavorable cervix remains a major obstacle to the successful induction of labor. Reported are results from an ongoing study of topical prostaglandin preparations used to effect preinduction cervical ripening. The current study compares the efficacy of 40 mg of prostaglandin (PG) F2 alpha versus 5 mg of PGE2, applied to the cervix in a methyltylose gel the night before attempted induction of labor. A prospective double-blind protocol was used similar to that which previously established the efficacy of the 5 mg of PGE2 preparation versus placebo at this institution. Results indicate the superiority of the PGE2 preparation as measured by change in Bishop score, Pitocin requirement, rate of cervical dilatation, and percentage of failed inductions. Cesarean section rates were similar in the two study groups, and no fetal or maternal morbidity was attributable to the preinduction ripening technique.

Cervix Uteri↗
PubMed1983

Nonrandom chromosomal changes in untreated retinoblastomas.

The karyotypic patterns of 15 retinoblastomas were examined. Five tumors were found to have two distinct stem lines and, therefore, the chromosomal patterns of 20 tumor cell lines are reported. Three nonrandom chromosomal changes, namely, a loss of a chromosome #13, the presence of an i(6p), or a trisomy of 1q were observed. The potential importance of these chromosomal changes in tumor development is discussed, particularly the loss of a chromosome #13 or the gain of an i(6p). At least one of the three chromosomal changes was found in 75% of the tumor lines analyzed.

Aneuploidy↗
PubMed1983

Invasive properties of primary pediatric neoplasms in vitro.

Primary solid tumors were mechanically and/or enzymatically disassociated, and the resulting suspensions of single cells and small clumps of cells were seeded onto three different substrates, i.e., tissue culture plastic, rat smooth muscle cells (SMCs), and SMC-derived extracellular matrix. Tests of the relative effectiveness of these substrates in supporting the survival and/or growth of ten different neoplasms demonstrated that only two explants remained viable for longer than 2 weeks when seeded onto tissue culture plastic while nine of the ten survived on biological substrates for 1 month or longer. Thus, tissue culture plastic was a poor substrate for primary pediatric neoplasms. In general, more than 80% of the most common solid neoplasms in childhood (brain tumor, neuroblastoma, renal tumor, rhabdomyosarcoma, osteogenic sarcoma, and Ewing's sarcoma) routinely survived or grew in long-term cultures when cultured onto SMCs or their matrix. Both substrates were effective in promoting survival and/or growth; however, cells of neuroblastomas and certain brain tumors showed a preference for a living smooth muscle substrate. Tumor cells maintained their characteristic cellular and subcellular morphology when compared with the histology of the in vivo neoplastic lesions. Light and electron microscopy of selected neoplasms cultured on SMCs for various time periods demonstrated areas of distinct cellular invasion and/or partial destruction of the SMC multilayers which correlated with the invasive potentials of the neoplasms in patients. Invasion and destruction of the SMCs were also noticed with quiescent tumor cell cultures, indicating that growth was not a necessary property of invasion. Several neoplasms were also capable of the degradation of connective tissue proteins as indicated by the hydrolysis of radiolabeled SMC matrices, but simple correlations between the extent of matrix degradation and invasive ability could not be drawn. The culture system described consistently provided for the survival and/or growth of the most common pediatric tumors for long time periods. Thus, basic biological properties of primary tumors, e.g., growth, invasive potentials, and differentiation capabilities, could be investigated routinely.

Cell Transformation, Neoplastic↗