Nuclei were prepared from mature and immature hen erythrocytes and incubated for RNA synthesis in the absence or in the presence of Sarkosyl. The in vitro labelled synthesized RNA was hybridized to specific 5' and 3' fragments of the chicken adult beta-globin gene to investigate the possible presence of RNA polymerase molecules bound to this gene in the form of transcriptional complexes. Surprisingly, such RNA polymerase B molecules were found located preferentially in the 5' end moiety of the beta-globin genes of mature erythrocytes, although they are apparently evenly distributed along the beta-globin genes of immature polychromatic erythrocytes. The significance of these observations with respect to (1) preferential DNaseI sensitivity of "genes which have been transcribed" and (2) control of transcription in eukaryotic cells is discussed.
Retinoid-X-receptor alpha (RXRalpha), a member of the nuclear receptor (NR) superfamily, is a ligand-dependent transcriptional regulatory factor. It plays a crucial role in NR signalling through heterodimerization with some 15 NRs. We investigated the role of RXRalpha and its partners on mouse skin tumor formation and malignant progression upon topical DMBA/TPA treatment. In mutants selectively ablated for RXRalpha in keratinocytes, epidermal tumors increased in size and number, and frequently progressed to carcinomas. As keratinocyte-selective peroxisome proliferator-activated receptor gamma (PPARgamma) ablation had similar effects, RXRalpha/PPARgamma heterodimers most probably mediate epidermal tumor suppression. Keratinocyte-selective RXRalpha-null and vitamin-D-receptor null mice also exhibited more numerous dermal melanocytic growths (nevi) than control mice, but only nevi from RXRalpha mutant mice progressed to invasive human-melanoma-like tumors. Distinct RXRalpha-mediated molecular events appear therefore to be involved, in keratinocytes, in cell-autonomous suppression of epidermal tumorigenesis and malignant progression, and in non-cell-autonomous suppression of nevi formation and progression. Our study emphasizes the crucial role of keratinocytes in chemically induced epidermal and melanocytic tumorigenesis, and raises the possibility that they could play a similar role in UV-induced tumorigenesis, notably in nevi formation and progression to melanoma.
We have obtained polyamine-compacted DNA and analyzed it by electron microscopy employing the method described by Dubochet, suitable for the study of complexes in which the main interactions are of ionic character. In addition, we have developed a simple biochemical method, based on the action of pancreatic DNase I, to demonstrate the condensation of DNA with spermidine. DNA-spermidine complexes are resistant to the action of DNase I, and there is a strong correlation between the presence of condensed DNA forms, both as toroids and as cylinders, and the insensitivity to DNase I activity. We have also shown that pBR322 DNA-spermidine complexes are transcriptionally active in the presence of Escherichia coli RNA polymerase. This supports the data concerning the biological activity of spermidine-condensed DNA.
Genital human Papillomavirus infection is common and only a minor fraction of infected subjects develop progressing cervical epithelial lesions or cancer. Bypassing local immune responses is important for the development of cervical cancer. In this work we determined the cytokine pattern in samples from patients with cervical cancer. Thus, we examined the local mRNA expression profile of helper T cell type 1 (Th1), Th2, and Th3 cytokines in HPV-positive cervical cancer biopsies by reverse transcription-polymerase chain reaction. Our data indicate that 80% of the tumors expressed low levels of CD4 mRNA, with all of them expressing higher CD8 mRNA levels. Most tumors expressed interleukin (IL)-4 and IL-10 mRNAs and, most importantly, all of them expressed transforming growth factor (TGF)-beta1 and interferon gamma mRNA. None of the tumors studied expressed IL-12, IL-6, or tumor necrosis factor (TNF) mRNA. Immunohistochemical analysis identified IL-10 only in tumor cells and koilocytic cells, but not in tumor-infiltrating lymphocytes, suggesting that IL-10-producing cells are those transformed by HPV. We found a correlation between immunostaining for IL-10 protein and the level of IL-10 mRNA expression. Moreover, supernatants from HPV-transformed cell cultures contained IL-10 and TGF- beta1. Our findings indicate a predominant expression of immunosuppressive cytokines, which might help downregulate tumor-specific immune responses in the microenvironment of the tumor. This information may be useful for cervical cancer immunotherapies or for therapeutic vaccine design against Human Papillomavirus.
Ether-à-go-go-1 (Eag1) potassium channels are potential tools for detection and therapy of numerous cancers. Here, we show human Eag1 (hEag1) regulation by cancer-associated factors. We studied hEag1 gene expression and its regulation by estradiol, antiestrogens, and human papillomavirus (HPV) oncogenes (E6/E7). Primary cultures from normal placentas and cervical cancer tissues; tumor cell lines from cervix, choriocarcinoma, keratinocytes, and lung; and normal cell lines from vascular endothelium, keratinocytes, and lung were used. Reverse transcription-PCR (RT-PCR) experiments and Southern blot analysis showed Eag1 expression in all of the cancer cell types, normal trophoblasts, and vascular endothelium, in contrast to normal keratinocytes and lung cells. Estradiol and antiestrogens regulated Eag1 in a cell type-dependent manner. Real-time RT-PCR experiments in HeLa cells showed that Eag1 estrogenic regulation was strongly associated with the expression of estrogen receptor-A. Eag1 protein was detected by monoclonal antibodies in normal placenta and placental blood vessels. Patch-clamp recordings in normal trophoblasts treated with estradiol exhibited potassium currents resembling Eag1 channel activity. Eag1 gene expression in keratinocytes depended either on cellular immortalization or the presence of HPV oncogenes. Eag1 protein was found in keratinocytes transfected with E6/E7 HPV oncogenes. Cell proliferation of E6/E7 keratinocytes was decreased by Eag1 antibodies inhibiting channel activity and by the nonspecific Eag1 inhibitors imipramine and astemizole; the latter also increased apoptosis. Our results propose novel oncogenic mechanisms of estrogen/ antiestrogen use and HPV infection. We also suggest Eag1 as an early indicator of cell proliferation leading to malignancies and a therapeutic target at early stages of cellular hyperproliferation. [Cancer Res 2009;69(8):3300-7]
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