Snapshots of replication through an abasic lesion; structural basis for base substitutions and frameshifts.

Dpo4 from S. Solfataricus, a DinB-like Y family polymerase, efficiently replicates DNA past an abasic lesion. We have determined crystal structures of Dpo4 complexed with five different abasic site-containing DNA substrates and find that translesion synthesis is template directed with the abasic site looped out and the incoming nucleotide is opposite the base 5' to the lesion.

Crystal structure of a benzo[a]pyrene diol epoxide adduct in a ternary complex with a DNA polymerase.

The first occupation-associated cancers to be recognized were the sooty warts (cancers of the scrotum) suffered by chimney sweeps in 18th century England. In the 19th century, high incidences of skin cancers were noted among fuel industry workers. By the early 20th century, malignant skin tumors were produced in laboratory animals by repeatedly painting them with coal tar.

Information and support needs of adolescent children of women with breast cancer.

Purpose/objectives: To elicit detailed descriptions of adolescents' information and support needs in response to their mothers' breast cancer.

Design: Exploratory, qualitative.

Setting: Four different outpatient and inpatient oncology settings in western Canada.

Escherichia coli DNA polymerase V subunit exchange: a post-SOS mechanism to curtail error-prone DNA synthesis.

DNA polymerase V consisting of a heterotrimer composed of one molecule of UmuC and two molecules of UmuD' (UmuD'2C) is responsible for SOS damage-induced mutagenesis in Escherichia coli. Here we show that although the UmuD'2C complex remains intact through multiple chromatographic steps, excess UmuD, the precursor to UmuD', displaces UmuD' from UmuD'2C by forming a UmuDD' heterodimer, while UmuC concomitantly aggregates as an insoluble precipitate. Although soluble UmuD'2C is readily detected when the two genes are co-transcribed and translated in vitro, soluble UmuD2C or UmuDD'C are not detected.

The 2002 Schering Lecture. Children's cancer symptom experiences: keeping the spirit alive in children and their families.

Despite the finding that each child and family experienced cancer in their own unique way, they all shared the need to maintain a sense of spirit. Just as the suffering united the families, so too did their sense of spirit. Talk of the spirit is not foreign in the pediatric oncology literature.

A different perspective to approaching cancer symptoms in children.

A sound and comprehensive knowledge base about symptoms in children experiencing cancer is necessary if health care professionals hope to effectively manage their symptoms. To date, there is still much to be discovered about how children with cancer and their families experience childhood cancer symptoms. Accordingly, a longitudinal qualitative study was undertaken between July 1998 and December 2000 to explore and describe the childhood cancer symptom course from the perspectives of children and their families.

Sequence context-dependent replication of DNA templates containing UV-induced lesions by human DNA polymerase iota.

Humans possess four Y-family polymerases: pols eta, iota, kappa and the Rev1 protein. The pivotal role that pol eta plays in protecting us from UV-induced skin cancers is unquestioned given that mutations in the POLH gene (encoding pol eta), lead to the sunlight-sensitive and cancer-prone xeroderma pigmentosum variant phenotype. The roles that pols iota, kappa and Rev1 play in the tolerance of UV-induced DNA damage is, however, much less clear.

129-derived strains of mice are deficient in DNA polymerase iota and have normal immunoglobulin hypermutation.

Recent studies suggest that DNA polymerase eta (poleta) and DNA polymerase iota (poliota) are involved in somatic hypermutation of immunoglobulin variable genes. To test the role of poliota in generating mutations in an animal model, we first characterized the biochemical properties of murine poliota. Like its human counterpart, murine poliota is extremely error-prone when catalyzing synthesis on a variety of DNA templates in vitro.

Replication of a cis-syn thymine dimer at atomic resolution.

Ultraviolet light damages DNA by catalysing covalent bond formation between adjacent pyrimidines, generating cis-syn cyclobutane pyrimidine dimers (CPDs) as the most common lesion. CPDs block DNA replication by high-fidelity DNA polymerases, but they can be efficiently bypassed by the Y-family DNA polymerase pol eta. Mutations in POLH encoding pol eta are implicated in nearly 20% of xeroderma pigmentosum, a human disease characterized by extreme sensitivity to sunlight and predisposition to skin cancer.

"Nothing is carved in stone!": uncertainty in children with cancer and their families.

Although more children are surviving childhood cancer, they and their families still face many new stressors and challenges. Understanding the experiences of childhood cancer in children and families is conditional upon building a sound and comprehensive knowledge base that is grounded in research. Accordingly, a longitudinal interpretive qualitative study was conducted to arrive at an understanding of children's and families' perspectives on having to experience the childhood cancer-symptom trajectory.

Localization of the deoxyribose phosphate lyase active site in human DNA polymerase iota by controlled proteolysis.

Human DNA polymerase iota (pol iota) is a member of the Y-family of low fidelity lesion bypass DNA polymerases. In addition to a probable role in DNA lesion bypass, this enzyme has recently been shown to be required for somatic hypermutation in human B-cells. We found earlier that human pol iota has deoxyribose phosphate (dRP) lyase activity and unusual specificity for activity during DNA synthesis, suggesting involvement in specialized forms of base excision repair (BER).

A substantive theory of Keeping the Spirit Alive: the Spirit Within children with cancer and their families.

Despite increasing survivorship, childhood cancer is nonetheless still a very traumatic phenomenon. Children and families must confront many new stressors and challenges. Understanding what families experience is essential if pediatric oncology nurses hope to provide sensitive and comprehensive care.

The risks and alternatives to physical punishment use with children.

Despite strong evidence of negative developmental outcomes resulting from the use of physical (or corporal) punishment with children, its use by parents and other caregivers is common. Such negative outcomes include child aggression, mental health issues, and physical abuse. Health care providers have a responsibility to promote disciplinary strategies that facilitate positive parent-children relationships and keep children's self-esteem and bodies healthy and intact.

Expectations and beliefs about children's cancer symptoms: perspectives of children with cancer and their families.

Purpose/objectives: To describe the childhood cancer symptom course experienced by children with cancer from the perspectives of the children and their families.

Design: Longitudinal, qualitative research approach.

Setting: The participants' homes and inpatient and outpatient pediatric cancer units in western Canada.

Localization of DNA polymerases eta and iota to the replication machinery is tightly co-ordinated in human cells.

Y-family DNA polymerases can replicate past a variety of damaged bases in vitro but, with the exception of DNA polymerase eta (poleta), which is defective in xeroderma pigmentosum variants, there is little information on the functions of these polymerases in vivo. Here, we show that DNA polymerase iota (poliota), like poleta, associates with the replication machinery and accumulates at stalled replication forks following DNA-damaging treatment. We show that poleta and poliota foci form with identical kinetics and spatial distributions, suggesting that localization of these two polymerases is tightly co-ordinated within the nucleus.

Structure-based interpretation of missense mutations in Y-family DNA polymerases and their implications for polymerase function and lesion bypass.

Our understanding of the molecular mechanisms of error-prone lesion bypass has changed dramatically in the past few years. The concept that the key participants in the mutagenic process were accessory proteins that somehow modified the ability of the cell's main replicase to facilitate bypass of normally blocking lesions has been replaced with one in which the replicase is displaced by a polymerase specialized in lesion bypass. The participants in this process remain the same, only their function has been reassigned.

Translesion replication of benzo[a]pyrene and benzo[c]phenanthrene diol epoxide adducts of deoxyadenosine and deoxyguanosine by human DNA polymerase iota.

Human DNA polymerase iota (poliota) is a Y-family polymerase whose cellular function is presently unknown. Here, we report on the ability of poliota to bypass various stereoisomers of benzo[a]pyrene (BaP) diol epoxide (DE) and benzo[c]phenanthrene (BcPh) DE adducts at deoxyadenosine (dA) or deoxyguanosine (dG) bases in four different template sequence contexts in vitro. We find that the BaP DE dG adducts pose a strong block to poliota-dependent replication and result in a high frequency of base misincorporations.

poliota-dependent lesion bypass in vitro.

Based upon phylogenetic relationships, the broad Y-family of DNA polymerases can be divided into various subfamilies consisting of UmuC (polV)-like; DinB (polIV/polkappa)-like; Rev1-like, Rad30A (poleta)-like and Rad30B (poliota)-like polymerases. The polIV/polkappa-like polymerases are most ubiquitous, having been identified in bacteria, archaea and eukaryotes. In contrast, the polV-like polymerases appear restricted to bacteria (both Gram positive and Gram negative).

Localization of DNA polymerases eta and iota to the replication machinery is tightly co-ordinated in human cells.

Y-family DNA polymerases can replicate past a variety of damaged bases in vitro but, with the exception of DNA polymerase eta (poleta), which is defective in xeroderma pigmentosum variants, there is little information on the functions of these polymerases in vivo. Here, we show that DNA polymerase iota (poliota), like poleta, associates with the replication machinery and accumulates at stalled replication forks following DNA-damaging treatment. We show that poleta and poliota foci form with identical kinetics and spatial distributions, suggesting that localization of these two polymerases is tightly co-ordinated within the nucleus.

Two distinct modes of RecA action are required for DNA polymerase V-catalyzed translesion synthesis.

SOS mutagenesis in Escherichia coli requires DNA polymerase V (pol V) and RecA protein to copy damaged DNA templates. Here we show that two distinct biochemical modes for RecA protein are necessary for pol V-catalyzed translesion synthesis. One RecA mode is characterized by a strong stimulation in nucleotide incorporation either directly opposite a lesion or at undamaged template sites, but by the absence of lesion bypass.

Perceived and performed infant care competence of younger and older adolescent mothers.

The investigators examined differences in perceived and performed infant care competence for younger (less than 17 years of age) and older (17 to 19 years of age) adolescent mothers. Associations were tested between perceived infant care competence measured at several time points and performed mothering at 12 to 18 months infant age. A convenience sample of 78 adolescent mothers was recruited from two major teaching hospitals in Winnipeg, Canada.

Escherichia coli DNA polymerase III can replicate efficiently past a T-T cis-syn cyclobutane dimer if DNA polymerase V and the 3' to 5' exonuclease proofreading function encoded by dnaQ are inactivated.

Although very little replication past a T-T cis-syn cyclobutane dimer normally takes place in Escherichia coli in the absence of DNA polymerase V (Pol V), we previously observed as much as half of the wild-type bypass frequency in Pol V-deficient (DeltaumuDC) strains if the 3' to 5' exonuclease proofreading activity of the Pol III epsilon subunit was also disabled by mutD5. This observation might be explained in at least two ways. In the absence of Pol V, wild-type Pol III might bind preferentially to the blocked primer terminus but be incapable of bypass, whereas the proofreading-deficient enzyme might dissociate more readily, providing access to bypass polymerases.

Replication restart in UV-irradiated Escherichia coli involving pols II, III, V, PriA, RecA and RecFOR proteins.

In Escherichia coli, UV-irradiated cells resume DNA synthesis after a transient inhibition by a process called replication restart. To elucidate the role of several key proteins involved in this process, we have analysed the time dependence of replication restart in strains carrying a combination of mutations in lexA, recA, polB (pol II), umuDC (pol V), priA, dnaC, recF, recO or recR. We find that both pol II and the origin-independent primosome-assembling function of PriA are essential for the immediate recovery of DNA synthesis after UV irradiation.