细胞技术

The study of metalloproteins by resonance Raman (RR) spectroscopy began two decades ago, with the publication by Long and coworkers of the first RR spectrum of the iron-sulfur protein rubredoxin (1,2). This simple spectrum, which contained only four bands attributed to the Fe-S stretching and ...

Murine embryonic stem (mES) cells are pluripotent cells derived from the inner cell mass of the preimplantation blastocyst. These cells are primitive and undifferentiated and have the potential to become a wide variety of specialized cell types. Mouse ES cells can be regarded as a versatile b ...

StemBase is a database of gene expression data obtained from stem cells and derivatives mainly from mouse and human using DNA microarrays and Serial Analysis of Gene Expression. Here, we describe this database and indicate ways to use it for the study the expression of particular genes in stem cells ...

DNA repair enzymes monitor a host’s genome for structural aberrations caused by exogenous damage (ionizing or UV radiation, chemical exposure) or spontaneous damage (deamination, oxidation, or base loss). Lack of repair at such sites can result in replication and transcription block ...

Nucleic-acid cleavage can be processive, with the enzyme moving from one site to the next in the polymer before dissociating from the substrate, or distributive, with partially cleaved substrates released to the medium after the initial reaction. Kinetics indicate that either mechani ...

The lumen of the endoplasmic reticulum (ER) is a highly specialized compartment in eukaryotic cells. Here, secretory and most membrane proteins are folded, covalently modified, and oligomerized with the assistance of specialized ER resident proteins (1). Perturbation of the ER lumen i ...

Nucleases catalyze the cleavage of phosphodiester bonds in nucleic acids. They range in size from divalent cations, such as Pb2+, which specifically cleaves tRNAPhe from yeast (1), and Mg2+, which specifically acts on squid tRNALys (2) to divalent cations complexed to chelating agents, for ex ...

Reverse transcription coupled with the polymerase chain reaction (RT-PCR), permits amplification of cellular RNA. Gene expression can be measured even when the message copy number is very low (1–10 copies per cell) (1) or the sample size is very small (1–1000 cells) (2,3). In RT-PCR, an RNA sample is pri ...

The most obvious functions of nucleases are nucleic-acid turnover and phosphate mobilization, but they also have more subtle roles. By its nature, nuclease activity may disrupt cellular information flow. Familiar examples include degradation of specific mRNAs, and bacterial rest ...

Allelic losses in the peritelomeric region of the long arm of human chromosome 6 (6q26–27) are associated with several human malignancies. These range from solid neoplasms such as ovarian carcinomas (1–8) to hematological cancers, among which B-cell non-Hodgkin’s lymphomas and acute ly ...

Integration is an essential step in the replication cycle of a retrovirus, such as the human immunodeficiency virus type 1 (HIV-1) (for a review, see ref. 1). After reverse transcription of the RNA genome, the DNA copy is transported into the nucleus and integrated in the host chromosome. The only viral e ...

Interferons (IFN) belong to a multigenic family of cytokines that activate the transcription of several genes through a signaling pathway involving cell-surface receptors (IFNAR), Janus kinases (JAK), and signal-transducing proteins (STAT), as comprehensively reviewed by St ...

Ribonuclease H (RNase H), first observed in extracts of calf thymus, is an apparently ubiquitous enzyme activity (1), which catalyzes the hydrolysis of RNA in RNA-DNA heteroduplexes (2). The two main classes (Type I and II) of eukaryotic RNase H have different biochemical requirements for maxi ...

RNA analysis and quantification require completely intact, nondegraded RNA samples to produce optimal results. Although nonenzymatic hydrolysis of phosphodiester bonds is favored by high temperature or pH and the presence of divalent cations (Mg2+, Mn2+), an RNA sample is most likely ...

Many cytokines alter the half-lives and stabilities of mRNAs for other cytokines (1) and enzymes that may be related to disease progression. For example, IL-1β stabilizes the mRNA for human interstitial collagenase-1 in normal fibroblasts, but not in breast cancer cells (2). Altering mRNA st ...

Ribonuclease inhibitor (RI) is a cytoplasmic protein of ∼50 kDa that tightly binds and inhibits ribonucleases (RNases) from the pancreatic superfamily (1). Diverse RNases with very limited sequence similarities, including RNase A, angiogenin, RNase-2 (also known as eosinophil-d ...

Barnase is a 110-residue extracellular ribonuclease produced by Bacillus amyloliquefaciens. The same organism produces an 89-residue polypeptide, barstar, which binds tightly to barnase and inhibits its potentially lethal RNase activity inside the cell. The three-dimenti ...

The enzyme RNase III catalyzes the hydrolysis of the phosphodiester bond between two nucleotides. The protein was discovered in 1968, when Robertson and coworkers isolated a double-stranded RNA (dsRNA) cleaving activity in Escherichia coli cells (1). A few years later, specific targets ...

Although evidence has been mounting since the 1930s that proteins could be reversibly denatured, it was not until the 1960s that the elegant experiments of Anfinsen on bovine pancreatic Ribonuclease A (RNase A) established that all the information needed for a protein to acquire three-dim ...

G protein-coupled receptors (GPCRs) make up the largest and most diverse family of membrane receptors in the human genome, relaying information about the presence of diverse extracellular stimuli to the cell interior. All known GPCRs share a common architecture of seven membrane-span ...