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The TRIP-Br1/p34 SEI-1 family proteins participate in cell cycle progression by coactivating E2F1-or p53-dependent transcriptional activation. Here, we report the identification of human CDCA4 (also know as SEI-3/Hepp) as a novel target gene of transcription factor E2F and as a repressor of E2F-dependent transcriptional activation. Analysis of CDCA4 promoter constructs showed that an E2F-responsive sequence in the vicinity of the transcription initiation site is necessary for the E2F1-4-induced activation of CDCA4 gene transcription. Chromatin immunoprecipitation analysis demonstrated that E2F1 and E2F4 bound to an E2F-responsive sequence of the human CDCA4 gene. Like TRIP-Br1/p34 SEI-1 and TRIP-Br2 (SEI-2), the transactivation domain of CDCA4 was mapped within C-terminal acidic region 175-241. The transactivation function of the CDCA4 protein was inhibited by E2F1-4 and DP2, but not by E2F5-8. Inhibition of CDCA4 transactivation activity by E2F1 partially interfered with retinoblastoma protein overexpression. Conversely, CDCA4 suppressed E2F1-3-induced reporter activity. CDCA4 (but not acidic region-deleted CDCA4) suppressed E2F1-regulated gene promoter activity. These findings suggest that the CDCA4 protein functions as a suppressor at the E2F-responsive promoter. Small interfering RNA-mediated knockdown of CDCA4 expression in cancer cells resulted in upregulation of cell growth rates and DNA synthesis. The CDCA4 protein was detected in several human cells and was induced as cells entered the G 1 /S phase of the cell cycle. Taken together, our results suggest that CDCA4 participates in the regulation of cell proliferation, mainly through the E2F/retinoblastoma protein pathway.

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In order to reveal the electrophysiological correlates of pulsatile LH release in ovariectomized rats, changes in multiple unit activity (MUA) in the arcuate nucleus (ARC), the medial preoptic area, the ventromedial nucleus, the anterior hypothalamic area and other areas of the brain were recorded in lightly anesthetized female rats. Rats were ovariectomized at least 7 weeks prior to the experiment. 0.1-ml blood samples were withdrawn from a cardiac catheter at 10-min intervals during the recording in order to measure the changes in the plasma LH concentration by radioimmunoassay. The LH concentration showed pulsatile changes under continuous intravenous infusion of thiopental sodium while cortical EEG was stable throughout the experiment. The firing rate in the middle part of the ARC (8 recordings) changed in parallel with the increase in the plasma LH concentration and was abruptly raised just prior to an increase in LH secretion. The number of MUA spike discharges per minute increased to 1.5–5 times that of the basal level. MUA started to increase 2–9 min prior to the LH rise and the high level of MUA lasted for 1–5 min. The firing rate in the ARC (14 recordings) and in other areas (54 recordings) recorded did not change periodically in parallel with the increase in LH. As these changes in MUA were localized in the ARC and were not reflected in cortical EEG, they might be specific local changes distinguished from generalized systemic effects involving the whole brain. These extreme increases in MUA seem to be due to the high activity either of neurons that secrete LH-RH or those that control the secretion of LH-RH.

The effects of electrical stimulation of the brain on the ovarian venous plasma concentrations of estradiol (E2) and progesterone (P) were investigated in female rats hypophysectomized and adrenalectomized at 1000 h on the day of proestrus. Stimulation was applied during the proestrous critical period under pentobarbital anesthesia, and contralateral ovarian venous blood was collected from 105-120 min after the stimulation. E2 and P concentrations, estimated by RIA, were significantly increased by stimulation of the medial basal prechiasmatic area (PVA), ventromedial hypothalamus, and areas in the mesencephalon and decreased by stimulation of the dorsal hippocampus, lateral amygdala, and mesencephalic areas. Ovarian blood flow was not affected by these stimulations. Ovarian nervotomy in the proestrous rats abolished E2 secretion induced by PVA stimulation. In intact proestrous rats, electrochemical stimulation of the PVA but not the preoptic suprachiasmatic area increased E2 and P concentrations, although stimulation of both areas commonly potentiated gonadotropin secretion. Present findings suggest that the efferent neural system from the brain to the ovaries is supplementary to the brain-pituitaryovarian hormonal mechanisms in the regulation of ovarian steroid secretion, and the system may be required for the adjustment of ovarian responsiveness and sensitivity to gonadotropins. In addition, evidence for neural feedback on basal FSH secretion in the ovarian-denervated proestrous rats is presented in this study. {Endocrinology 109: 136, 1981) I T HAS been demonstrated in rats that the cyclic alteration of ovarian steroid biosynthesis (1) and secretion (2, 3) are temporally related to the cyclic changes of gonadotropin secretion throughout the estrous cycle. The administration of gonadotropins to cyclic rats increased or decreased ovarian biosynthetic activity (1), and the effects were altered qualitatively and quantitatively during the estrous cycle (1, 4). However, it is still obscure whether the cyclic changes in ovarian steroid synthesis and release depend only upon gonadotropin secretion. Stimulation of the dorsal hippocampus (d-HPC) during the estrous cycle changed steroid biosynthetic activity without affecting gonadotropin secretion (4) or pituitary stalk blood LHRH concentration (5). More recently, d-HPC stimulation was shown to induce alterations in ovarian estrogen and progestin biosyntheses in pituitary-lesioned rabbits pretreated with 20a-hydroxyprogesterone (6). The above findings indicate the existence of other mechanisms besides the gonadotropin regulation of ovarian steroid synthesis and release.Recently, adrenergic and cholinergic projections to the