Adhesion Molecules-28

Advances and Experimental-1

Aging-9

Agricultural Biotechnology-37

Angiogenesis-29

Antisense-4

Apoptosis-49

Atherosclerosis-12

Autoimmunity-69

Bacterial Virulence-18

Bioinformatics-13

BioMaterials-18

Biosurfactants-1

Biotechnology-99

Cancer Genetics-25

Cancer Metastasis-19

Cell Biology-16

Cell Cycle-34

Cell Metabolism-327

Channels and Transporters-79

Chaperones-11

Circadian Rhythms-13

Coagulation-14

Cytokines/Growth Factors-52

Development-223

DNA-56

DNA Surveillance and Repair-42

Drug Design-17

Endocrine-66

Evolution-33

Extracellular Matrix-30

Gastroenterology-52

Gene Expression-178

Gene Therapy-53

Heart-61

Heat Shock Proteins-19

Hematology-11

Immunology-93

Infectious Disease-71

Ischemia-Reperfusion-33

Leptin and Leptin Antagonists-1

Medical-12

MHC-17

Mitochondria-17

Molecular Biology-13

Molecular Complexes and Signaling-1

Nanomedicine-30

Neurodegenerative Disease-72

Neuropharmacology-112

Neuroscience-38

Nucleus-15

Oncogenes-8

Oncology-87

Parasitic Disease-12

Pharmacogenomics-14

Prebiotic Evolution-2

Protein-12

Reproductive Biology-59

RNA-152

Signal Transduction-186

Stem Cells-80

Surgery-37

T-Cell Activation-12

Tissue Engineering-116

Transplant-51

Vaccines-82

Viruses-85

Chapter category: Viruses

Bacteriophage SPP1 DNA Packaging

Chapter authors:
Anja Droge and Paulo Tavares

SPP1 is a virulent double-stranded DNA (dsDNA) phage that infects the Gram-positive bacterium Bacillus subtilis strain 168. SPP1 belongs to the Siphoviridae family. The virion is composed of an icosahedral, isometric capsid (~60 nm diameter) and a long, flexible, noncontractile tail.1 The phage head encloses the mature SPP1 chromosome, which is a linear double-stranded DNA molecule of ~45.9 kbp size.2,3 Replication of the SPP1 genome produces DNA concatemers from which single chromosomes are cleaved and encapsidated into preformed procapsids. SPP1 packages its DNA by a headful packaging mechanism, a strategy first described for bacteriophage T4.4 As for phages P22 or P1, in case of SPP1 DNA packaging starts by recognition and cleavage of a defined nucleotide sequence termed pac.5,6 The concatemeric DNA is then translocated unidirectionally to the viral capsid interior. When the level of capsid DNA headfilling reaches a threshold amount (headful) a second endonucleolytic cleavage occurs. This second cleavage, the “headful cut”, defines the size of the packaged DNA. In contrast to pac cleavage the sequence independent headful cut is imprecise. The size of mature SPP1 DNA therefore varies for about 6% around the average chromosome size of 45.9 kb.7,8 Since the genome of SPP1 encompasses 44,007 bp,9 the chromosomes generated by headful cut are terminally redundant (~4.1%). While the first round of packaging is initiated by a sequence specific cut at pac, the second and subsequent packaging events start from the DNA end generated by the headful cut of the previous packaging event. Therefore this strategy generates a population of phage chromosomes that are partially circularly permutated and terminally redundant (Fig. 1). Terminal redundancy of the packaged DNA molecule is essential for circularisation of the viral genome by homologous recombination after its injection in the host cell at the beginning of a new infection cycle.

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