In This Issue
BIOCHEMISTRY
ATP transporter identified
The storing of neurotransmitters in tiny intracellular vesicles, and their subsequent expulsion from the cell, forms the basis for communication between neurons and endocrine cells. Given that the concentration of neurotransmitters inside the vesicles is greater than in the surrounding fluid, these molecules must be actively pumped into the storage bodies. To date, four types of transporters are known to move monoamine, acetylcholine, inhibitory amino acids, and glutamate into specific vesicles. Keisuke Sawada et al. have identified a new type of vesicular nucleotide transporter protein, SLC17A9, that concentrates ATP into adrenal chromaffin granules and synaptic vesicles. This long-sought nucleotide transporter may be the missing link in purine-related chemical transmission within the cell. SLC17A9 is expressed in astrocytes, and homologues are found in both vertebrates and invertebrates. — B.T.
Transfer protein SLC17A9 colocalized with synaptotagmin.
“Identification of a vesicular nucleotide transporter” by Keisuke Sawada, Noriko Echigo, Narinobu Juge, Takaaki Miyaji, Masato Otsuka, Hiroshi Omote, Akitsugu Yamamoto, and Yoshinori Moriyama (see pages 5683–5686)
CELL BIOLOGY
Magnesium deficiency accelerates cellular senescence
Magnesium is essential for a wide range of biological processes because many enzymes require the element for proper function. More than half of all Americans do not receive enough magnesium in their diet, resulting in a deficiency that can lead to increased risk for several aging-related diseases, including high blood pressure, cardiovascular disease, diabetes, and osteoporosis. To better understand how a lack of magnesium may contribute to these illnesses, David Killilea and Bruce Ames studied the long-term effects of moderate magnesium deficiency in human fibroblasts—cells that provide a structural framework for many tissues in the body. Although the deficient fibroblasts survived and divided normally, they experienced accelerated aging. The authors linked the cells' premature senescence in part to shortened telomeres, the repetitive DNA sequences that protect the ends of chromosomes. Disruption of proper telomere function has been shown to play a role in aging and carcinogenesis. The authors suggest that, through this mechanism, chronic magnesium deficiency could promote, or exacerbate, age-related diseases. — F.A.
Senescence biomarker (green) under magnesium-deficient conditions.
“Magnesium deficiency accelerates cellular senescence in cultured human fibroblasts” by David W. Killilea and Bruce N. Ames (see pages 5768–5773)
GENETICS
Fingering knockouts
Disrupting the expression of a single gene is crucial in understanding its function. Yolanda Santiago et al. report that a new method for knocking out gene expression could speed up an important but time-consuming process that is featured in many molecular biology applications. Current laboratory techniques for gene disruption produce a small number of cells with both copies of the desired gene missing, resulting in months of laborious screening. To develop a more accurate and efficient targeting method, Santiago et al. co-opted zinc finger nucleases. These enzymes cut DNA precisely within the gene targeted for elimination. The cut is healed by the natural DNA repair system inside cells, a process that often results in a small chunk of DNA being deleted. Taking advantage of this imperfect repair, the authors engineered zinc finger nucleases to target a specific gene in hamster cells. The targeted disruption and subsequent repair resulted in cells missing the intended gene and facilitated rapid isolation of multiple independent knockout cell lines. In addition, the screening process did not require selection markers that could hamper the use of these cell lines in downstream applications like therapeutic protein production. — T.H.D.
“Targeted gene knockout in mammalian cells by using engineered zinc-finger nucleases” by Yolanda Santiago, Edmond Chan, Pei-Qi Liu, Salvatore Orlando, Lin Zhang, Fyodor D. Urnov, Michael C. Holmes, Dmitry Guschin, Adam Waite, Jeffrey C. Miller, Edward J. Rebar, Philip D. Gregory, Aaron Klug, and Trevor N. Collingwood (see pages 5809–5814)
MEDICAL SCIENCES
HPV vaccine shows promise in mice
Genital human papillomavirus (HPV) infections, which typically manifest as genital warts and anogenital growths, are the most common sexually transmitted diseases in the United States. If untreated, a small percentage of these infections lead to cancer. HPV has been detected in 99.7% of cervical carcinomas worldwide, suggesting that the virus causes the cancer and that the disease could be prevented with a prophylactic HPV vaccination. Hannah Alphs et al. tested whether vaccinating mice with a highly conserved segment of the L2 capsid protein (L2 17–36 peptide) taken from HPV16 would provide broad protection against HPV16 and other cancer-causing strains. When L2 17–36 peptide was linked to a T helper epitope (P25) and the Toll-like receptor-2 ligand dipalmitoyl-S-glyceryl cysteine and delivered either subcutaneously or intranasally, the mice generated a potent neutralizing antibody response that protected them from both HPV16 and HPV45, the strains that account for ≈50% and ≈10%, respectively, of cervical cancer cases worldwide. — B.T.
Vaccinated mice challenged by HPV45.
“Protection against heterologous human papillomavirus challenge by a synthetic lipopeptide vaccine containing a broadly cross-neutralizing epitope of L2” by Hannah H. Alphs, Ratish Gambhira, Balasubramanyam Karanam, Jeffrey N. Roberts, Subhashini Jagu, John T. Schiller, Weiguang Zeng, David C. Jackson, and Richard B. S. Roden (see pages 5850–5855)
PLANT BIOLOGY
The origin of the “tea scent” in roses
A mutation in which a gene is duplicated and then altered at a single location is responsible for the distinct smell of “tea roses,” researchers report. The major component of the scent is dimethoxytoluene (DMT), produced by the orcinol O-methyltransferases OOMT1 and OOMT2, which add methyl groups to orcinol's two hydroxyl groups. OOMT1 and OOMT2 are nearly identical in structure, differing significantly only at their active site, where OOMT2 has a phenylalanine residue in place of tyrosine. Gabriel Scalliet et al. previously found that some European roses possess OOMT gene homologues, but that only Chinese roses express the proteins. Using genetic manipulation techniques, the authors reversed the mutations and showed that this switched the enzymes' function. The authors then expanded their catalogue of OOMT-like genes in roses, assaying 5 Chinese and 13 European rose species with PCR amplification. Scalliet et al. found 73 potentially functional genetic homologues, with every species possessing at least one; however, only Chinese rose genomes contained OOMT1-like genes. Phylogenetic analysis found all OOMT1 genes clustered in a single, late-emerging clade, suggesting that OOMT1 evolved through gene duplication of OOMT2 and subsequent mutation, according to the authors. — K.M.
Rosa chinensis cv. Old Blush, the major Chinese ancestor of modern roses.
“Scent evolution in Chinese roses” by Gabriel Scalliet, Florence Piola, Christophe J. Douady, Stéphane Réty, Olivier Raymond, Sylvie Baudino, Karim Bordji, Mohammed Bendahmane, Christian Dumas, J. Mark Cock, and Philippe Hugueney (see pages 5927–5932)
