Genetic origins of amino acids 1.1 Constituents and organisation of DNA DNA (deoxyribonucleic acid) is the genetic coding scheme used by all living organisms to pass on the hereditary programme to the next generation. DNA consists of two cross-linked polynucleotide chains, having an overall length of about 2 metres, which, for eukaryotes, is stored within the nucleus of a cell. The nucleus occupies about 10% of the cell volume and is isolated from the cytoplasm by the nuclear envelope, which consists of inner and outer bi-layer lipid membranes.
With the use of photoresponsive T7 promoters tethering two 2¢-methylazo-benzenes or 2¢,6¢-dimethylazobenzenes, highly efficient photoregulation
of DNA transcription was obtained. After UV-A light irradiation
(320–400 nm), the rate of transcription with T7 RNA polymerase and a
photoresponsive promoter involving two 2¢,6¢-dimethylazobenzenes was
10-fold faster than that after visible light irradiation (400–600 nm).
The folding of eukaryotic DNA into the 30 nm fibre comprises the first
level of transcriptionally dormant chromatin. Understanding its structure
and the processes of its folding and unfolding is a prerequisite for under-standing the epigenetic regulation in cell differentiation.
Nucleosome positioning is an important mechanism for the regulation of
eukaryotic gene expression. Folding of the chromatin fiber can influence
nucleosome positioning, whereas similar electrostatic mechanisms govern
the nucleosome repeat length and chromatin fiber folding in vitro.
The chi (v)and psi(w) subunits of Escherichia coliDNA
polymerase III formaheterodimer that is associatedwith the
ATP-dependent clamp-loadermachinery. InE. coli,thev:w
heterodimer serves as a bridge between the clamp-loader
complex and the single-strandedDNA-binding protein. We
determined the crystal structure of thev:wheterodimer at
Folding of DNA into chromatin is mediated by binding to
histones such as H4; association of DNA with histones is
regulated by covalent histone modifications,e.g. acetylation,
methylation,andbiotinylation.We sought to identifyamino-acid residues that are biotinylated in histone H4,and to
determine whether acetylation and methylation of histones
affect biotinylation. Synthetic peptides spanning fragments
of human histone H4 were biotinylated enzymatically using
biotinidase. Peptide-bound biotin was probed with strept-avidin–peroxidase....
Murine double minute 2 (MDM2) protein exhibits many diverse biochemi-cal functions on the tumour suppressor protein p53, including transcrip-tional suppression and E3 ubiquitin ligase activity. However, more recent
data have shown that MDM2 can exhibit ATP-dependent molecular chap-erone activity and directly mediate folding of the p53 tetramer. Analysing
the ATP-dependent function of MDM2 will provide novel insights into the
evolution and function of the protein.
Tyrosyl-DNA phosphodiesterase (TDP) cleaves the phosphodiester bond linking the active site tyrosine residue of topoisomerase I with the 3¢ terminus of DNA in topoisomerase I–DNA complexes which accumulate during treatment of cancer with camptothecin. In yeast, TDP mutation confers a 1000-fold hypersensitivity to camptothecin in the presence of an additional mutation of RAD9 gene [Pouliot, J.J., Yao, K.C., Robertson, C.A. & Nash, H.A. (1999) Science 286, 552–555].
Plants play important role for human beings since the ancient times. Plants have their
own whole different world which includes entire kingdom of life. Plants are the most
essential part of organism in the world. Nobody can imagine any life without plants
involved in their life. When humans started building colonies and getting civilized
their dependency on plants increased by several folds. Today plants are even more
important due to the increased demand of their different uses. During their
development civilizations based on their use and growing cycle plants have been
Desmoplastic melanoma (DM) is an unusual, non-pigmented, sclerosing variant of spindle
cell malignant melanoma that can range in appearance from sarcomatoid to scar-like lesion.
Cytomorphologic features described on FNA include a moderate cellularity with pleomorphic
spindle cells occurring singly and in small aggregates. The spindle cells exhibit plump
nuclei with deep grooves and folds, coarse and clumped chromatin, and inconspicuous to
multiple, prominent nucleoli, along with naked spindly nuclei. Intranuclear cytoplasmic
inclusions are rare.
Recently, a novel uracil-DNA-degrading factor protein (UDE) was identi-fied inDrosophila melanogaster, with homologues only in pupating insects.
Its unique uracil-DNA-degrading activity and a potential domain organiza-tion pattern have been described.
Cell survival depends not only on the ability to repair damaged DNA
but also on the capability to perform DNA replication on unrepaired or
imperfect templates. Crucial to this process are specialized DNA polym-erases belonging to the Y family. These enzymes share a similar catalytic
fold in their N-terminal region, and most of them have a less-well-con-served C-terminus which is not required for catalytic activity.
DnaG is the primase that lays down RNA primers on single-stranded
DNA during bacterial DNA replication. The solution structure of the
DnaB-helicase-binding C-terminal domain ofEscherichia coliDnaG was
determined by NMR spectroscopy at near-neutral pH. The structure is a
rare fold that, besides occurring in DnaG C-terminal domains, has been
described only for the N-terminal domain of DnaB.
To identify artificial DNA segments that can stably express transgenes in the
genome of host cells, we built a series of curved DNA segments that mimic a
left-handed superhelical structure. Curved DNA segments of 288 bp (T32)
and 180 bp (T20) were able to activate transcription from the herpes simplex
virus thymidine kinase (tk) promoter by approximately 150-fold and 70-fold,
respectively, compared to a control in a transient transfection assay in
We have studied the stability of the histone-like,
DNA-binding protein HU from the hyperthermophilic
eubacteriumThermotoga maritimaand its E34D mutant by
differential scanningmicrocalorimetry and CDunder acidic
conditions at various concentrations within the range of
2–225lMof monomer. The thermal unfolding of both
proteins is highly reversible and clearly follows a two-state
dissociation/unfolding model from the folded, dimeric state
to the unfolded, monomericone.
There is widespread acceptance that cationic antimicrobial peptides, apart
from their membrane-permeabilizing⁄disrupting properties, also operate
through interactions with intracellular targets, or disruption of key cellu-lar processes. Examples of intracellular activity include inhibition of
DNA and protein synthesis, inhibition of chaperone-assisted protein
folding and enzymatic activity
Guanine-rich DNA sequences have the ability to fold into four-stranded
structures called G-quadruplexes, and are considered as promising antican-cer targets. Although the G-quadruplex structure is composed of quartets
and interspersed loops, in the genome it is also flanked on each side by
Accumulations of aggregated proteins are a key feature of the pathology of
all of the major neurodegenerative diseases. Amyotrophic lateral sclerosis
(ALS) was brought into this fold quite recently with the discovery of TDP-43
(TAR DNA binding protein, 43 kDa) inclusions in nearly all ALS cases.