The Role of miRNAs as Key Regulators in the Neoplastic Microenvironment.

The neoplastic microenvironment has been recognized to play a critical role in the development of cancer. Although a large body of evidence has established the importance of the cancer microenvironment, the manners of crosstalk between it and the cancer cells still remains unclear. Emerging mechanisms of communication include microRNAs (miRNAs). miRNAs are small noncoding RNA molecules that are involved in the posttranscriptional regulation of mRNA. Both intracellular and circulating miRNAs are differentially expressed in cancer and some of these alterations have been correlated with clinical patient outcomes. The role of miRNAs in the tumor microenvironment has only recently become a focus of research, however. In this paper, we discuss the influence of miRNAs on the tumor microenvironment as it relates to cancer progression. We conclude that miRNAs are a critical component in understanding invasion and metastasis of cancer cells.

Limitations of animal models of Parkinson's disease.

Most cases of Parkinson's disease (PD) are sporadic. When choosing an animal model for idiopathic PD, one must consider the extent of similarity or divergence between the physiology, anatomy, behavior, and regulation of gene expression between humans and the animal. Rodents and nonhuman primates are used most frequently in PD research because when a Parkinsonian state is induced, they mimic many aspects of idiopathic PD. These models have been useful in our understanding of the etiology of the disease and provide a means for testing new treatments. However, the current animal models often fall short in replicating the true pathophysiology occurring in idiopathic PD, and thus results from animal models often do not translate to the clinic. In this paper we will explain the limitations of animal models of PD and why their use is inappropriate for the study of some aspects of PD.

Differential distribution of factors involved in pre-mRNA processing in the yeast cell nucleus.

The yeast cell nucleus has previously been shown to be divided into two regions by a variety of microscopic approaches. We used antibodies specific for the 2,2,7-trimethylguanosine cap structure of small nuclear ribonucleic acids (snRNAs) and for a protein component of small nuclear ribonucleoprotein particles to identify the distribution of small nuclear ribonucleoprotein particles within the yeast cell nucleus. These studies were performed with the fission yeast Schizosaccharomyces pombe and the budding yeast Saccharomyces cerevisiae. By using immunofluorescence microscopy and immunoelectron microscopy, most of the abundant snRNAs were localized to the portion of the nucleus which has heretofore been referred to as the nucleolus. This distribution of snRNAs is different from that found in mammalian cells and suggests that the nucleolar portion of the yeast nucleus contains functional domains in addition to those associated with RNA polymerase I activity.

Multiple phosphorylated forms of the product of the fission yeast cell division cycle gene cdc2+.

The 34 kilodalton protein product (p34) of the cdc2+ cell cycle control gene of Schizosaccharomyces pombe was expressed in bacteria. Monoclonal antibodies raised against this protein are capable of immunoprecipitating p34cdc2 from yeast lysates. Immunoprecipitates of [35S]methionine- and [32P]orthophosphate-labeled p34cdc2 were analyzed by two-dimensional gel electrophoresis. The cdc2+ gene product is homogeneous in size but resolves into seven species of differing charge. At least four of these species are phosphorylated. Phosphoamino acid analysis reveals that phosphorylation occurs mainly on threonine residues. The pattern of p34 phosphorylation is unaltered at the nonpermissive temperature in strains carrying temperature sensitive alleles of weel-50 and ran1-114 or in a strain overproducing the ran1+ gene product.

Characterization of DNA sequences associated with residual nuclei of Saccharomyces cerevisiae.

We have used two different approaches to determine whether particular DNA sequences are specifically associated with high-salt-treated residual nuclei of Saccharomyces cerevisiae. First, libraries of yeast DNA in phage lambda were probed with nick-translated total nuclear or residual nuclear DNA from unsynchronized yeast cells. None of the plaques gave a significantly stronger or weaker signal with the residual nuclear probe than with the total nuclear probe. Second, DNA was purified from whole nuclei or residual nuclei which had been isolated from cells in G1, G1/S, early S, or nuclear division. This DNA was "dot-blotted" and then probed with specific yeast DNA sequences. Ribosomal DNA was 2- to 3-fold enriched in residual nuclei in late G1, G1/S, and early S, and 2 microns plasmid DNA sequences were 3- to 5-fold depleted during nuclear division and early G1. However, ARS1, TRP1, CEN6, and a telomere sequence were neither enriched nor depleted at any time during the cell cycle.

Isolation and initial characterization of residual nuclear structures from yeast.

Residual nuclear structures have previously been isolated from a wide range of eukaryotic organisms. When nuclei are isolated from Saccharomyces cerevisiae and then treated with 1.95 M NaCl and DNase I, sedimentable residual structures are obtained similar in several respects to structures isolated from organisms previously studied. These yeast residual nuclear structures retain less than 7% of nuclear DNA, less than 17% of nuclear RNA and less than 50% of nuclear proteins. Electron microscopy suggests that these structures are derived from the nuclear interior and are composed of a sparse fibrogranular network. Replicating DNA is preferentially bound to these yeast residual nuclear structures, just as it is to residual nuclear structures from other organisms.

A possible mechanism by which SV40 T-antigen stimulates rRNA synthesis.

Binding of SV40 T-antigen to RNA polymerase I could account for the observation that T-antigen stimulates rRNA synthesis and that nucleoli do not stain for T-antigen. Two tests were performed to detect binding: a) RNA polymerase I was isolated and assayed in the presence of T-antigen; polymerase activity was enhanced. b) RNA polymerase I and T-antigen were mixed and then T-antigen complement fixation assays performed, complement fixation was not inhibited.