DNA packaging and cutting by phage terminases: Control in phage T4 by a synaptic mechanism

Black, Lindsay W.

doi:10.1002/bies.950171206

Cited by 67 publications

(39 citation statements)

References 52 publications

(15 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These enzymes, which are required for packaging DNA (76), interact with each other (77). Other proteins, such as the ss DNA binding protein gp 32, or T4 gene 46-47 proteins, appear to be important in all recombination pathways, but different interactions with other proteins are important for their roles in different pathways.…”

Section: Discussionmentioning

confidence: 99%

Two recombination-dependent DNA replication pathways of bacteriophage T4, and their roles in mutagenesis and horizontal gene transfer

Mosig

Gewin

Luder

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

. In wild-type T4, timing of these pathways is integrated with the developmental program and related to transcription and packaging of DNA. In primase mutants, which are defective in origin-dependent lagging-strand DNA synthesis, the late pathway can bypass the lack of primers for lagging-strand DNA synthesis. The exquisitely regulated synthesis of endo VII, and of two proteins from its gene, explains the delay of recombination-dependent DNA replication in primase (as well as topoisomerase) mutants, and the temperature-dependence of the delay. Other proteins (e.g., the singlestranded DNA binding protein and the products of genes 46 and 47) are important in all recombination pathways, but they interact differently with other proteins in different pathways. These homologous recombination pathways contribute to evolution because they facilitate acquisition of any foreign DNA with limited sequence homology during horizontal gene transfer, without requiring transposition or site-specific recombination functions. Partial heteroduplex repair can generate what appears to be multiple mutations from a single recombinational intermediate. The resulting sequence divergence generates barriers to formation of viable recombinants. The multiple sequence changes can also lead to erroneous estimates in phylogenetic analyses.The purpose of looking back is not, of course, merely to obtain satisfaction from reflecting on past triumphs; rather, it is to discover as many clues as possible to the likely developments of the future.Glenn T. Seaborg T he tight interrelationship between homologous recombination and DNA replication was first evident in T4 and the related T-even phages. Because DNA of T4 and its host E. coli differ in base composition and modifications and because the host DNA is rapidly degraded after phage infection, molecular aspects of T4 replication and recombination could be readily investigated by biochemical, biophysical, and genetic methods. Early characterization of mutations in most essential genes (1) and the almost complete dependence of replication and recombination on phage-encoded proteins (2) allowed analyses of recombination and replication proteins, as well as ''reality checks'' of results obtained with genetic and biochemical methods (3). The following idiosyncrasies of T4 chromosomes revealed the importance of DNA ends and recombination-dependent DNA replication. Ends of T4 chromosomes are cut during packaging from branched concatemers, which are generated by recombination-dependent replication. A ''headful mechanism'' packages a complete genome and Ϸ3% DNA repeated at each end as ''terminal redundancy,'' thereby generating the random circular permutation of chromosomal ends (4). Some smaller T4 particles, formed because of assembly errors, package incomplete genomes whose ends are also randomly circularly permuted (5). Multifactor crosses revealed stimulation of recombination by their DNA ends, regardless of map positions (5, 6). Moreover, different segregation patterns of alleles in patch vs. splice re...

show abstract

Section: Discussionmentioning

confidence: 99%

Two recombination-dependent DNA replication pathways of bacteriophage T4, and their roles in mutagenesis and horizontal gene transfer

Mosig

Gewin

Luder

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…Plasmid GST-UL56C was generated by digestion of pRC/CMV-UL56 (7) and pGEX-5X-1 (Amersham Biosciences) as described previously (23). The 1.5-kb fragment encoding the carboxyl-terminal half of HCMV pUL56 (amino acids 446 -850) was ligated in-frame into pGEX-5X-1, yielding pGEX-UL56C.…”

Section: Methodsmentioning

confidence: 99%

“…The large subunit catalyzes the ATP-dependent translocation of genomic DNA into the bacteriophage procapsids and the small unit binds and cleaves concatenated DNA (21,22). Mutations in any of the encoding genes lead to an accumulation of empty procapsids (proheads) and DNA concatemers (23). Rao et al (24) demonstrated that the ATPase activity is associated with the large terminase subunit gp17 of bacteriophage T4.…”

mentioning

confidence: 99%

ATPase Activity of the Terminase Subunit pUL56 of Human Cytomegalovirus

Hwang¹,

Bogner²

2002

Journal of Biological Chemistry

View full text Add to dashboard Cite

Herpesviral DNA packaging is a complex process resulting in unit-length genomes packed into preformed procapsids. This process is believed to be mediated by two packaging proteins, the terminase subunits. In the case of double-stranded DNA bacteriophages, the translocation of DNA was shown to be an energy-dependent process associated with an ATPase activity of the large terminase subunit. In the case of human cytomegalovirus it was not known which protein has the ability to hydrolyze ATP. In this study we expressed human cytomegalovirus terminase subunits, pUL89 and the carboxyl-terminal half of pUL56, as GST fusion proteins and purified these by affinity chromatography. ATPase assays demonstrated that the enzymatic activity is exclusively associated with pUL56. The characterization of the ATP hydrolysis showed that the enzymatic reaction is a fast process, whereas the spontaneous ATP decay followed slow kinetics. Interestingly, although pUL89 did not show any ATPase activity, it was capable of enhancing the UL56-associated ATP hydrolysis. Furthermore, a specific association of in vitro translated pUL89 with the carboxyl-terminal half of GST-UL56C was detected. This interaction was confirmed by co-immunoprecipitations of infected cells. Our results clearly demonstrated that (i) both terminase subunits interact with each other and (ii) the subunit pUL56 has an ATPase activity. Human cytomegalovirus (HCMV)1 DNA replication results in the formation of large head-to-tail DNA concatemers. The subsequent maturation into unit-length molecules involves site-specific cleavage at sequence motifs (pac motifs) located within the a sequence of the terminal and internal repeat segments (1-4). Unit-length genomes are then encapsidated into preassembled capsids. DNA-packaging is a complex biological process. While it is commonly accepted that ATP hydrolysis is the driving force behind it, the molecular mechanisms of DNA translocation and genome packaging remain unclear. In general, the following five steps are involved. (i) The recognition of concatemeric DNA by a specific protein (complex) able to (ii) bind and cut the DNA at specific sequence motifs (packaging signals, e.g. pac1 and pac2), (iii) translocation of the DNAprotein complex into the procapsid, (iv) packaging of one unitlength genome, and (v) completion of the packaging process by cutting off excess DNA at the portal region (5-7).Recently, we have demonstrated that the HCMV pUL56 gene product (pUL56), the homolog of the HSV-1 open reading frame UL28, is associated with sequence-specific binding of DNA containing packaging motifs leading to the suggestion that pUL56 plays a key role in DNA packaging (7-9). Comparable results were reported of the HSV-1 pUL28, demonstrating a direct interaction of pUL28 with DNA containing the pac1 motif (10). Furthermore, by the use of viral mutants it was demonstrated that the deletion of pUL28 leads to nuclear accumulation of naked nucleocapsids and uncleaved concatemeric DNA (11, 12). In addition, it has been noted that the HCMV UL...

show abstract

“…2B). These events should occur in adjacent terminal repetitions in a controlled manner such as the synaptic mechanism proposed for T4 (Black 1995). In f-29, DNA replication proceeds by a proteinpriming mechanism from either end of the linear molecule by strand displacement to generate mature molecules with gp3 covalently linked to the 5 0 -termini (Mellado et al 1980).…”

Section: Dna Processingmentioning

confidence: 99%

Phage DNA packaging

1997

View full text Add to dashboard Cite

Phage DNA packaging occurs by DNA translocation into a preformed protein shell-a prohead-with the aid of a packaging enzyme or a terminase. The packaging enzyme is composed of two subunits: the large subunit has ATP-binding, prohead binding, and DNA cleavage activities, and the small subunit is a DNA binding protein. DNA translocation is driven by ATP hydrolysis. In general, phage DNA replication mechanisms lead to the accumulation of concatemers. Concatemers are processed to mature DNA during and depending upon DNA packaging. This review will focus on the molecular mechanism of concatemer processing and the coupling of ATP hydrolysis to DNA translocation.

show abstract

DNA packaging and cutting by phage terminases: Control in phage T4 by a synaptic mechanism

Cited by 67 publications

References 52 publications

Two recombination-dependent DNA replication pathways of bacteriophage T4, and their roles in mutagenesis and horizontal gene transfer

Two recombination-dependent DNA replication pathways of bacteriophage T4, and their roles in mutagenesis and horizontal gene transfer

ATPase Activity of the Terminase Subunit pUL56 of Human Cytomegalovirus

Phage DNA packaging

Contact Info

Product

Resources

About