Biomedical subjects

Purificación Muñoz

Publications and source records attributed to Purificación Muñoz.

6 recordsLinked to original sources

PubMed2006

Role of the TRF2 telomeric protein in cancer and ageing.

Telomeres are the special heterochromatin that forms the ends of chromosomes, consisting of TTAGGG repeats and associated proteins. Telomeres protect the ends from degradation and recombination, and are essential for chromosomal stability. Both a minimal length of telomere repeats and the telomere-binding proteins are required for telomere protection. Telomerase is a DNA polymerase that specifically elongates telomeres, in this way regulating telomere length and function. A minimal telomere length is required to maintain tissue homeostasis. On one hand, critically short telomeres trigger loss of cell viability and premature death in mice deficient for telomerase activity. Furthermore, altered functioning of telomerase and telomere-interacting proteins is present in some human premature ageing syndromes and cancer. A new mouse model with critically short telomeres has been generated by overexpressing the TRF2 telomere-binding protein, K5-TRF2 mice. These mice show short telomeres in the presence of telomerase activity, leading to premature aging and increased cancer. Short telomeres in TRF2 mice can be rescued in the absence of the XPF nuclease, indicating that this enzyme rapidly degrades telomeres in the presence of increased TRF2 expression. K5-TRF2 mice represent a new tool to understand the consequences of critical telomere shortening a telomerase-proficient genetic background, more closely resembling human cancer and aging pathologies.

Aging↗

PubMed2005

XPF nuclease-dependent telomere loss and increased DNA damage in mice overexpressing TRF2 result in premature aging and cancer.

TRF2 is a telomere-binding protein that has a role in telomere protection. We generated mice that overexpress TRF2 in the skin. These mice had a severe phenotype in the skin in response to light, consisting of premature skin deterioration, hyperpigmentation and increased skin cancer, which resembles the human syndrome xeroderma pigmentosum. Keratinocytes from these mice were hypersensitive to ultraviolet irradiation and DNA crosslinking agents. The skin cells of these mice had marked telomere shortening, loss of the telomeric G-strand overhang and increased chromosomal instability. Telomere loss in these mice was mediated by XPF, a structure-specific nuclease involved in ultraviolet-induced damage repair and mutated in individuals with xeroderma pigmentosum. These findings suggest that TRF2 provides a crucial link between telomere function and ultraviolet-induced damage repair, whose alteration underlies genomic instability, cancer and aging. Finally, we show that a number of human skin tumors have increased expression of TRF2, further highlighting a role for TRF2 in skin cancer.

Aging, Premature↗

PubMed2004

Role of human Ku86 in telomere length maintenance and telomere capping.

The role of Ku86 at telomeres has been extensively studied in various organisms; however, a role for Ku86 at human telomeres was unknown because Ku86 deletion is lethal for human cells. Here, we used small interference RNA to decrease Ku86 protein levels in human cells. An approximately 50% reduction in the amount of Ku86 protein was achieved 72 hours after transfection with Ku86-specific small interference RNAs. This decrease in Ku86 levels resulted in a rapid loss of cell viability characterized by increased apoptosis and decreased mitotic index in the cell population. Importantly, Ku86 knockdown was concomitant with a significant loss of telomeric sequences and with increased chromosomal aberrations, including chromatid-type fusions involving telomeric sequences. These findings demonstrate a role for Ku86 in regulating telomere length and telomere capping in human cells, which, in turn, could impact on cancer and aging.

Animals↗

PubMed2004

The giant protein HERC1 is recruited to aluminum fluoride-induced actin-rich surface protrusions in HeLa cells.

HERC1 is a very large protein involved in membrane traffic through both its ability to bind clathrin and its guanine nucleotide exchange factor (GEF) activity over ARF and Rab family GTPases. Herein, we show that HERC1 is recruited onto actin-rich surface protrusions in ARF6-transfected HeLa cells upon aluminum fluoride (AlF(4)(-)) treatment. Moreover, the fact that HERC1 overexpression does not stimulate protrusion formation in the absence of AlF(4)(-), in conditions where ARNO does, indicates that HERC1 is not acting as an ARF6-GEF in this system, but that instead its recruitment takes place downstream of ARF6 activation. Finally, we suggest a phosphoinositide-binding mechanism whereby HERC1 may translocate to these protrusions.

ADP-Ribosylation Factor 6↗

PubMed2003

Interaction between HERC1 and M2-type pyruvate kinase.

HERC proteins are characterized by having one or more RCC1-like domains as well as a C-terminal HECT domain in their amino acid sequences. This has led researchers to suggest that they may act as both guanine nucleotide exchange factors and E3 ubiquitin ligases. Here we describe a physical interaction between the HECT domain of HERC1, a giant protein involved in intracellular membrane traffic, and the M2 isoform of glycolytic enzyme pyruvate kinase (M2-PK). Partial colocalization of endogenous proteins was observed by immunofluorescence studies. This interaction neither induced M2-PK ubiquitination nor affected its enzymatic activity. The putative significance of the association is discussed.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Role of mammalian Rad54 in telomere length maintenance.

The homologous recombination (HR) DNA repair pathway participates in telomere length maintenance in yeast but its putative role at mammalian telomeres is unknown. Mammalian Rad54 is part of the HR machinery, and Rad54-deficient mice show a reduced HR capability. Here, we show that Rad54-deficient mice also show significantly shorter telomeres than wild-type controls, indicating that Rad54 activity plays an essential role in telomere length maintenance in mammals. Rad54 deficiency also resulted in an increased frequency of end-to-end chromosome fusions involving telomeres compared to the controls, suggesting a putative role of Rad54 in telomere capping. Finally, the study of mice doubly deficient for Rad54 and DNA-PKcs showed that telomere fusions due to DNA-PKcs deficiency were not rescued in the absence of Rad54, suggesting that they are not mediated by Rad54 activity.

Animals↗