RESUMO
Transcription of the Ig H chain germline transcripts is a prerequisite for class switching. Expression of the epsilon germline transcript is induced by IL-4 and requires the integrity of a composite IL-4 response element. The element is bound by the IL-4-inducible transcription factor Stat6 and one or more members of the CAAT/enhancer-binding protein (C/EBP) family, a constitutively expressed class of transcription factors. Here, we show that Stat6 and C/EBP beta cooperate to synergistically activate transcription from the epsilon element. The effect was most pronounced in lymphoid cells, and the activation domains of both proteins were required to achieve this synergy. Although other members of the C/EBP family are able to bind the element, very little cooperativity was seen with C/EBP alpha and none with C/EBP gamma. In fact, C/EBP gamma was able to inhibit IL-4-induced reporter activity. Stat6 and C/EBP beta bind the IL-4 response element simultaneously. The fast dissociation rate apparent when Stat6 binds this DNA element alone is slowed when C/EBP beta binds at the neighboring site. These data suggest a mechanism whereby C/EBP beta stabilizes Stat6 binding at this element, thereby increasing the likelihood that both of their activation domains will interact, possibly with other factors, to activate transcription in an IL-4-dependent manner.
Assuntos
Proteínas de Ligação a DNA/fisiologia , Regulação da Expressão Gênica/imunologia , Cadeias épsilon de Imunoglobulina/genética , Proteínas Nucleares/fisiologia , Regiões Promotoras Genéticas/imunologia , Transativadores/fisiologia , Proteínas Estimuladoras de Ligação a CCAAT , Linhagem Celular , DNA/metabolismo , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/metabolismo , Regulação para Baixo/genética , Regulação para Baixo/imunologia , Sinergismo Farmacológico , Humanos , Cadeias épsilon de Imunoglobulina/metabolismo , Interleucina-4/genética , Interleucina-4/metabolismo , Interleucina-4/fisiologia , Proteínas Nucleares/química , Proteínas Nucleares/metabolismo , Ligação Proteica/genética , Ligação Proteica/imunologia , Estrutura Terciária de Proteína , Fator de Transcrição STAT6 , Transativadores/química , Transativadores/metabolismo , Ativação Transcricional/imunologiaRESUMO
We have isolated and sequenced a cDNA that encodes mouse endothelin-1 (ET-1). The putative protein contains 202 amino acids corresponds to the prepro-form of ET-1. Twenty-one amino acids sequence of the putative mature ET-1 was identical with that of rat, porcine, bovine, and human. In situ hybridization histochemistry indicate that ET-1 mRNA was expressed in several hypothalamic nuclei including the suprachiasmatic nucleus (SCN) in rodent brain.
Assuntos
DNA Complementar/química , Endotelinas/genética , Núcleo Supraquiasmático/metabolismo , Sequência de Aminoácidos , Animais , Sequência de Bases , Bovinos , Humanos , Hibridização In Situ , Camundongos , Dados de Sequência Molecular , RNA Mensageiro/análise , Ratos , SuínosRESUMO
A new antimicrobial quinolone (-)BO-2367, (-)-7-[(1R*, 2R*, 6R*)-2-amino-8-azabicyclo[4.3.0.]-non-3-en-8-yl]-1- cyclopropyl-6,8-difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid, strongly inhibited both mammalian and bacterial topoisomerase II. The IC50 values of (-)BO-2367 against the DNA relaxation activity of L1210 topoisomerase II and the supercoiling activities of Escherichia coli gyrase and Micrococcus luteus gyrase were 3.8, 0.5, and 1 microM, respectively. This compound enhanced double-stranded DNA cleavage mediated by topoisomerase II not only with purified enzyme, but also with intact L1210 cells. All these activities of (-)BO-2367 were more than 2-fold stronger than those of VP-16. Intriguingly, (+)BO-2367, which has an enantiomeric substituent at the C7 position of (-)BO-2367, did not affect the activity of the mammalian topoisomerase II, while it inhibited E. coli gyrase. Intraperitoneal injection of (-)BO-2367 at 0.08 mg/kg increased the lifespan of CDF1 female mice bearing ascitic L1210 leukemia by 2.4 times, and subcutaneous injection at 1.25 mg/kg completely inhibited the growth of colon 26 carcinoma implanted subcutaneously. These results suggest that (-)BO-2367 is a potent antitumor agent which targets topoisomerase II. These enantiomers should be a useful tool for studying drug-topoisomerase II interactions.
