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replicon
A Replicon in genetics is a region of DNA or RNA, that replicates from a single origin of replication. TERM 2
replication fork
DEFINITION 2 is a structure that forms within the nucleus during DNA replication. It is created by helicases, which break the hydrogen bonds holding the two DNA strands together TERM 3
leading strand
DEFINITION 3 the strand of DNA being replicated continuously. It is the strand that is being continuously polymerized toward the replication fork. All DNA synthesis occurs 5'-3'. The original DNA strand must be read 3'-5' to produce a 5'-3' nascent strand the leading strand is formed as a polymerase "reads" the template DNA and continuously adds nucleotides to the 3' end of the elongating strand TERM 4
lagging strand
DEFINITION 4 The lagging strand grows in the direction opposite to the movement of the growing fork. It grows away from the replication fork and it is synthesized discontinuously. Because the strand is growing away from the replication fork, it must be replicated in fragments because the Primase (that adds the RNA primer) has to wait until the fork opens to be able to add the primer. The RNA Polymerase reaches the origin of replication and stops replication until a new RNA primer is placed. These fragments of DNA produced on the lagging strand are called Okazaki fragments. TERM 5
Okazaki fragments
DEFINITION 5 are short molecules of single-stranded DNA that are formed on the lagging strand during DNA replication.
SV
unenveloped icosahedral virion with a closed circular dsDNA genome Inside the cell nucleus, the cellular RNA polymerase II acts to promote early gene expression The small and large T antigens result from this Once in the nucleus the large T antigen binds three viral DNA sites, I, II, and III. Binding of sites I, and II autoregulates early RNA synthesis. Binding site I initiates DNA replication at the origin of replication TERM 7
SV
DEFINITION 7 Unenveloped icosahedral virion with a closed circular dsDNA genome Inside the cell nucleus, the cellular RNA polymerase II acts to promote early gene expression The small and large T antigens result from this Once in the nucleus the large T antigen binds three viral DNA sites, I, II, and III. Binding of sites I, and II autoregulates early RNA synthesis. Binding site I initiates DNA replication at the origin of replication TERM 8
SV
DEFINITION 8 Like other polyomaviruses, SV40 is a DNA virus that has the potential to cause tumors, but most often persists as a latent infection. SV40 is believed to suppress the transcriptional properties of the tumor-suppressing p53 in humans through the SV40 Large T-antigen p53 is responsible for initiating regulated cell death ("apoptosis"), or cell cycle arrest when a cell is damaged A mutated p53 gene may contribute to uncontrolled cellular proliferation, leading to a tumor. TERM 9
SV40 large T antigen
DEFINITION 9 is a hexamer protein that is a proto-oncogene derived from the polyomavirus SV40 which is capable of transforming a variety of cell types. The transforming activity of TAg is due in large part to its perturbation of the retinoblastoma (pRB) and p53 tumor suppressor proteins. SV40 DNA replication is initiated by binding of large T-antigen to the origin region of the genome. TERM 10
Pcna
DEFINITION 10 The protein encoded by this gene is found in the nucleus and is a cofactor of DNA polymerase delta. The encoded protein acts as a homotrimer and helps increase the processivity of leading strand synthesis during DNA replication. In response to DNA damage, this protein is ubiquitinated and is involved in the RAD6-dependent DNA repair pathway. Two transcript variants encoding the same protein have been found for this gene. Pseudogenes of this gene have been described on chromosome 4 and on the X chromosome.
ITR
sequences
these sequences is their ability to form a hairpin, which contributes to so-called self-priming that allows primase- independent synthesis of the second DNA strand. were also shown to be required for both integration of the AAV DNA into the host cell genome TERM 17
adenovirus
DEFINITION 17 icosahedral viruses composed of a nucleocapsid and a double-stranded linear DNA genome. TERM 18
capsid
DEFINITION 18 A capsid is the protein shell of a virus. It consists of several oligomeric structural subunits made of protein called protomers The capsid encloses the genetic material of the virus. he majority of viruses have capsids with either helical or icosahedral structure. TERM 19
adenovirus
DEFINITION 19 Adenoviruses are medium-sized (90-100 nm), nonenveloped (without an outer lipid bilayer) icosahedral viruses composed of a nucleocapsid and a double-stranded linear DNA genome. TERM 20
beta hairpin
DEFINITION 20 The beta hairpin structural motif is the simplest protein motif involving two beta strands that look like a hairpin. structural motif is the simplest protein motif involving two beta strands that look like a hairpin.
Semiconservative replication
describes the mechanism by which DNA is replicated in all known cells. Semiconservative replication would produce two copies that each contained one of the original strands and one new strand. TERM 22
poxvirus
DEFINITION 22 Linear, the linear genome is flanked by inverted terminal repeat (ITR) sequences which are covalently-closed at their extremities. TERM 23
proliferating
DEFINITION 23 Proliferating Cell Nuclear Antigen, commonly known as PCNA, is a protein that acts as a processivity factor for DNA polymerase in eukaryotic cells. TERM 24
E2f
DEFINITION 24 The Rb tumour suppressor protein (pRb) binds to the E2F- 1 transcription factor preventing it from interacting with the cell's transcription machinery. E2F target genes encode proteins involved in DNA replication When cells are not proliferating, E2F DNA binding sites contribute to transcriptional repression. TERM 25
membrane protein
DEFINITION 25 is a protein molecule that is attached to, or associated with the membrane of a cell or an organelle.
Ribonucleoprotein (RNP)
is a nucleoprotein that contains RNA, i.e. it is an association that combines ribonucleic acid and protein together RNPs play an important role in influenzavirus A replication. The viral RNA is transcribed into mRNAs by the RNA polymerase attached to the RNPs. TERM 32
Proteolysis
DEFINITION 32 is the directed degradation of proteins by cellular enzymes called proteases or by intramolecular digestion. Removal of N-terminal methionine residues after translation. Removal of the signal sequence of peptides after their transport through a membrane Separation of viral proteins that were translated from a polycistronic mRNA Digestion of proteins from foods as a source of amino acids Degradation of unneeded or damaged proteins for example cyclins at different stages of the cell cycle. TERM 33
secretory pathway
DEFINITION 33 The secretory pathway is a series of steps a cell uses to move proteins out of the cell; a process known as secretion. TERM 34
signal recognition particle
DEFINITION 34 is an abundant, cytosolic, universally conserved ribonucleoprotein (protein-RNA complex) that recognizes and targets specific proteins to the endoplasmic reticulum in eukaryotes and the plasma membrane in prokaryotes. TERM 35
stop transfer signal
DEFINITION 35 encountered in the nascent protein.
Glycosylation
refers to the enzymatic process that attaches glycans to proteins, lipids, or other organic molecules is a form of co-translational and post-translational modification TERM 37
glycoform
DEFINITION 37 A protein isoform is any of several different forms of the same protein. TERM 38
N-linked glycosylation
DEFINITION 38 is a type of linkage that is mainly formed between sugar molecules in biochemistry. TERM 39
oligosaccharides
DEFINITION 39 is a saccharide polymer containing a small number (typically two to ten) of component sugars, also known as simple sugars (monosaccharides). TERM 40
molecular chaperone
DEFINITION 40 are proteins that assist the non-covalent folding or unfolding and the assembly or disassembly of other macromolecular structures, but do not occur in these structures when the structures are performing their normal biological functions having completed the processes of folding and/or assembly.
basolateral domain
a polarized cell is the surface of the plasma membrane that forms its basal and lateral surfaces. It faces towards the interstitium, and away from the lumen. TERM 47
lipid rafts
DEFINITION 47 The plasma membrane of cells is made of a combination of glycosphingolipids and protein receptors organized in glycolipoprotein microdomains termed lipid rafts. TERM 48
lipid droplet
DEFINITION 48 Remarkably, lipid droplets appear to be the sites of viral genome replication lipid droplets are attached to the ER membrane. TERM 49
CYCLINS
DEFINITION 49 are a family of proteins that control the progression of cells through the cell cycle by activating cyclin-dependent kinase enzymes. TERM 50
viral
oncogene
DEFINITION 50 An oncovirus is a virus that can cause cancer. This term originated from studies of acutely-transforming retroviruses
permissive
When a cell or host is defined as permissive in virology, it refers to the fact that the virus is able to circumvent host defenses and is able to replicate. TERM 52
c-myc
DEFINITION 52 Myc is a regulator gene that codes for a transcription factor. A mutated version of Myc is found in many cancers, which causes Myc to be constitutively (persistently) expressed This leads to the unregulated expression of many genes, some of which are involved in cell proliferation and results in the formation of cancer. TERM 53
c-erb-b
DEFINITION 53 HER2 is a member of the epidermal growth factor receptor (EGFR/ErbB) family. Amplification or over-expression of this gene has been shown to play an important role in the pathogenesis and progression of certain aggressive types of breast cancer and in recent years it has evolved to become an important biomarker and target of therapy for the disease. TERM 54
p
DEFINITION 54 p53 (also known as protein 53 or tumor protein 53), is a tumor suppressor protein that in humans is encoded by the TP53 gene. it regulates the cell cycle functions as a tumor suppressor that is involved in preventing cancer preventing genome mutation. TERM 55
Rb
DEFINITION 55 is a tumor suppressor protein that is dysfunctional in several major cancers One function of pRb is to prevent excessive cell growth by inhibiting cell cycle progression until a cell is ready to divide. human papillomaviruses, bind and inactivate pRb, this can lead to cancer. pRb binds and inhibits transcription factors of the E2F family
src
is oncogenic as it triggers uncontrolled growth in abnormal host cells encodes a tyrosine kinase that attaches phosphate groups to the amino acid tyrosine in host cell proteins. src gene was taken up by RSV and incorporated into its genome conferring it with the advantage of being able to stimulate uncontrolled mitosis of host cells, providing abundant cells for fresh infection TERM 62
v-SRC
DEFINITION 62 It was found that the v-src gene in RSV is required for the formation of cancer and that the other genes have no role in oncogenesis. TERM 63
c-src
DEFINITION 63 C-src tyrosine kinase, is a human membrane-anchored tyrosine kinase protein encoded by the CSK gene. This discovery changed the current thinking about cancer from a model wherein cancer is caused by a foreign substance (a viral gene) to one where a gene that is normally present in the cell can cause cancer. TERM 64
Avian Leucosis
Virus
DEFINITION 64 virus is an endogenous retrovirus that infects and can lead to cancer in chickens; experimentally it can infect other species of birds and mammals. ASLV replicates in chicken embryo fibroblasts, the cells that contribute to the formation of connective tissues the virus is transcribed from RNA to DNA TERM 65
alimentary tract
DEFINITION 65 The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus.
tissue tropism
is a term most often used in virology to define the cells and tissues of a host which support growth of a particular virus.
