Cellular & molecular biology research最新文献

NFI is a family of transcription factors that binds discrete nucleotide sequence and regulates transcriptional activity of genes. Transactivation occurs through proline-rich sequences. Among the genes whose transcriptional activity is regulated are those expressed in a cell-type specific manner. This suggests the possible existence of NFI proteins with distinct properties. With the use of the polymerase chain reaction technique, we have cloned and analyzed the activity of three spliced variants of NFI (class X) genes in murine cells. Expression vectors containing the regulatory regions of these proteins fused to the DNA binding domain of the yeast transcription factor GAL4 helped identify both negative and positive regulatory domains. In the context of the whole NFI/X proteins, spliced variants lacking the positive regulatory sequences functioned as repressors, whereas those containing both regulatory domains functioned as weak activators. With the identification of the negative domain in the NFI/X proteins, we demonstrate here a novel regulatory feature of these proteins in positive and negative modulation of gene expression.

A variety of conflicting results appeared in the literature concerning the effect of dominant oncogenes on the sensitivity to irradiation and to anticancer agents in a number of cell lines of human and animal origin. In this report we provide evidence supporting the hypothesis that the tumor suppressor gene p53 and the apoptosis suppressor gene bcl2 modulate the effect of dominant oncogenes and that the effect of dominant oncogenes on resistance or sensitivity is dependent on the balance between the expression of p53 and bcl2.

Artificial conditions of incubation light have been found to have profound effects on hatchability of chicken and turkey eggs. It has been shown that illumination of eggs throughout the incubation period reduces hatching time by approximately 20 h compared with dark incubation. Experiments carried out in the present study using different intensities of fluorescent light for first 40 h of incubation in ovo indicate significant acceleration of morphogenesis in chick embryos as determined by cell population analysis. The maximum acceleration of growth was observed at intensity range of 1500-3000 lux without any adverse effects as compared with dark-incubated controls (p < 0.01).

Tuberous sclerosis (TS) is a genetically heterogeneous disease characterized by the widespread appearance of nonmalignant growths that affect multiple organ systems. A TS disease-determining gene, located at 16p13.3 and designated TSC2, has recently been cloned. In this report, the murine TSC2 homologue was cloned and characterized. cDNA clones encompassing the entire murine TSC2 transcript were isolated. Sequence analysis revealed a high degree of homology between the deduced amino acid sequence of the murine and human gene products. Northern blot surveys demonstrated widespread TSC2 expression which was subject to developmental regulation in a tissue-specific manner. Although high levels of TSC2 transcripts were observed in many adult tissues, protein analyses are required to determine whether functional tuberin protein is synthesized. Reverse transcription-polymerase chain reaction analyses identified at least six regions of alternative splicing, several of which modified putative regulatory motifs in the deduced amino acid structure of the TSC2 protein.

The mouse Grg gene encodes a 197 amino acid nuclear protein homologous to the amino-terminal domain of the product of the groucho (gro) gene of the Drosophila Enhancer of split complex. Recent work has suggested that the gro protein functions as a transcriptional corepressor during Drosophila development. We therefore examined possible roles of the mouse Grg protein in DNA binding and in vitro transcription. No sequence-specific DNA binding activity was detected by polymerase chain reaction-DNA binding site selection nor was the glutamine-rich Grg protein capable of acting as an activation domain in an in vivo transactivation assay. However, depletion of Grg protein from HeLa nuclear extracts inhibited the in vitro transcription activity of the extracts. We suggest that Grg protein may interact with components of the basal transcription machinery.

In this review, the immune system is described as a physiological system in its functions and relations with other organs. Hence, communications are mediated by common receptors and cytokines. The immunophysiology is a bidirectional system where the immune system is influenced by endocrine apparatus and vice versa. At the cellular level, we have attempted to define this "cross-talk" by proposing one- or two-signal models, where the first signal is mediated via binding of hormones or neurohormones to the lymphocytes and the second signal is generated by binding of the antigen to the recognition sites or of cytokines to their lymphocyte receptors. The physiological reality of these interrelationships is discussed.

We examined the androgenic regulation of protein kinase CK1 in rat ventral prostate cytosolic and chromatin fractions. On androgen deprivation, CK1 in both the nuclear and cytoplasmic compartments decreases slowly at a similar rate. Stimulation of regrowth in the prostate does not evoke an early differential modulation in the CK1 because it increased in both the cytosol and chromatin only by 24 h after androgenic stimulus. These changes in CK1 relate to its proposed role in cell regulation at mitosis and differ from those in protein kinase CK2 that demonstrates rapid modulations in the nuclear compartment under similar conditions.

Identification of the genetic basis for congenital heart defects has been a topic of inquiry for pediatric cardiologists for many years. Any genetic model proposed must account for three often puzzling features of congenital heart diseases, namely the high population incidence, the less than Mendelian recurrence risk, and low concordance rates of heart lesions within individual families. A multifactorial or polygenic inheritance model has been used to explain these observations. Although this model has been serviceable, it does not adequately explain the phenotypic variability within families. Further, the emphasis on teratogenic influences has not led to the elucidation of pathogenetic mechanisms. The multifactorial model should be modified to include the role of chance as originally proposed by Kurnit. Once the role of chance is acknowledged, the phenotypic variability of congenital heart diseases becomes less problematic, and the multifactorial model gives way to a model in which single genes are capable of producing congenital heart disease. Through recent work in animal models and humans, it is now clear that single congenital heart disease genes can be identified that produce phenotypic variability in families that is similar to that seen in the population as a whole. Examples demonstrating recent progress in the search for major congenital heart disease genes are discussed.