The structural domains contributing to ion permeation and selectivity in K channels were examined in inward-rectifier K(+) channels ROMK2 (Kir1.1b), IRK1 (Kir2.1), and their chimeras using heterologous expression in Xenopus oocytes. Patch-clamp recordings of single channels were obtained in the cell-attached mode with different permeant cations in the pipette. For inward K(+) conduction, replac...

Progression through the cell cycle is dependent on the sequential expression of cyclins, which combine with cyclin-dependent kinases (cdks) to form active kinases. The transition from G1 to S phase is dependent on D cyclins in complex with cdk4 or cdk6 and cyclin E complexed with cdk2. One target of G1 cyclins is the retinoblastoma susceptibility protein (Rb). Rb is a transcriptional repressor ...

The retinoblastoma protein pRb plays a pivotal role in G(1)- to S-phase cell cycle progression and is among the most frequently mutated gene products in human cancer. Although much focus has been placed on understanding how the A/B pocket and COOH-terminal domain of pRb cooperate to relieve transcriptional repression of E2F-responsive genes, comparatively little emphasis has been placed on the ...

Epigenetic marks that specify silent heterochromatic domains in eucaryotic genomes include methylation of histone H3 lysine 9. Strikingly, active loci in the vicinity of silent domains are sometimes characterized by acetylation of histone H3 lysine 9, suggesting that the balance between these two competitive modifications is important for the establishment of specific chromatin structures. Some...

Unlike mammalian and yeast cells, little is known about how plants regulate G1 progression and entry into the S phase of the cell cycle. In mammalian cells, a key regulator of this process is the retinoblastoma tumor suppressor protein (RB). In contrast, G1 control in Saccharomyces cerevisiae does not utilize an RB-like protein. We report here the cloning of cDNAs from two Zea mays genes, RRB1 ...

Precise control of the mitotic cell cycle is a critical feature of eukaryotic life. In humans, mutations in cell cycle regulatory genes lead to the uncontrolled cell proliferation and tumor formation associated with the most dreaded of all diseases, cancer. E2F transcription factors are key components of an elaborate mechanism of cell cycle control in higher eukaryotes. For example, the promote...

A model of learning in a highly active and competitive environment is presented here. This paper posits that learning, under these conditions, can be characterized as accommodating examples produced by the Constrained Example Generation (CEG) process. The role of the"CEG process in the LRCEG system is demonstrated by a typical learning scenario. I INTRODUCTION This paper Introduces an emerging ...

A Redirection Botnet (RBnet) is a vast collection of compromised computers (called bots) used as a redirection/proxy infrastructure and under the control of a botmaster. We present the design, implementation and evaluation of a system called Redirection Botnet Seeker (RB-Seeker) for automatic detection of RBnets by utilizing three cooperating subsystems. Two of the subsystems are used to genera...