April 2009 Volume 16 Number 4, pp 345 - 451
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EDITORIAL
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Pressing information p345
One aim in science communication is to make the general public more
aware of the breakthroughs and insights basic science research
provides. Our press office gives us one route to help achieve that
goal.
doi:10.1038/nsmb0409-345
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NEWS AND VIEWS
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miR-9 and TLX: chasing tails in neural stem cells pp346 - 347
Development and maintenance of an organism require the precise
spatiotemporal orchestration of stem cell proliferation and
differentiation. In neurogenesis, a microRNA and an orphan nuclear
receptor comprise a negative feedback loop that regulates neural
stem cell fate.
Ahmet M Denli, Xinwei Cao and Fred H Gage
doi:10.1038/nsmb0409-346
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A tipping point for mistranslation and disease pp348 - 349
Two papers present strong evidence that the codon-anticodon
interaction is poised on a tipping point so that, given a nudge, the
tRNA can insert the wrong amino acid into the growing polypeptide
chain, leading to translational fidelity loss.
Paul Schimmel and Min Guo
doi:10.1038/nsmb0409-348
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At the (3') end, you'll turn to meiosis pp350 - 351
Many cellular fates are determined by different genetic programs,
but the regulation of cellular differentiation is still not well
understood. Besides the possible control exerted by the activity
and combination of transcription factors, there are multiple RNA
processing mechanisms, ensuring differential gene expression.
Alberto Moldon and Jose Ayte
doi:10.1038/nsmb0409-350
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Yeast as budding stem cells? p351
Ines Chen
doi:10.1038/nsmb0409-351
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RESEARCH HIGHLIGHTS
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Research highlights p352
doi:10.1038/nsmb0409-352
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ARTICLES
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Bases in the anticodon loop of tRNAAlaGGC prevent misreading
pp353 - 358
The conserved A32-U38 pair in the anticodon loop of tRNAAlaGGC is
now shown to be important for accurate decoding. Using tRNAAla
variants in this pair in an in vitro translation system showed
that some variants could decode both the cognate and a near-cognate
codons with high efficiency. These mutants tRNA were toxic in vivo,
supporting the biological relevance of this accuracy determinant.
Hiroshi Murakami, Atsushi Ohta and Hiroaki Suga
doi:10.1038/nsmb.1580
Abstract: http://links.ealert.nature.com/ctt?kn=57&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Article: http://links.ealert.nature.com/ctt?kn=51&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
A sequence element that tunes Escherichia coli tRNAAlaGGC to ensure
accurate decoding pp359 - 364
The conserved A32-U38 pair in the anticodon loop of tRNAAlaGGC is
now shown to be important for accurate decoding. Pre-steady state
kinetic analyses of mutants in A32-U38 show that they can efficiently
decode near-cognate codons, with a mismatch in any of the three
positions, pointing to the role of such conserved sequence elements
in suppressing misreading during translation.
Sarah Ledoux, Mikolaj Olejniczak and Olke C Uhlenbeck
doi:10.1038/nsmb.1581
Abstract: http://links.ealert.nature.com/ctt?kn=79&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Article: http://links.ealert.nature.com/ctt?kn=53&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
A feedback regulatory loop involving microRNA-9 and nuclear receptor
TLX in neural stem cell fate determination pp365 - 371
MicroRNAs are involved in post-transcriptional regulation of gene
expression. Data now indicate that miR-9 targets the nuclear receptor
TLX and vice versa, thus proposing a regulatory circuit linked to the
switch between neural progenitor proliferation and differentiation.
Chunnian Zhao, GuoQiang Sun, Shengxiu Li and Yanhong Shi
doi:10.1038/nsmb.1576
Abstract: http://links.ealert.nature.com/ctt?kn=52&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Article: http://links.ealert.nature.com/ctt?kn=99&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
TRF2 functions as a protein hub and regulates telomere maintenance by
recognizing specific peptide motifs pp372 - 379
TRF2 is a member of the telosome/shelterin complex, which helps
maintain telomere integrity. Using an oriented peptide library
based on a previously identified TRF2-interaction region to define
a consensus sequence for binding, new proteins have been identified
as TRF2 interactors and implicated in telomeric functions. This
suggests that TRF2 acts as a hub for recruiting different proteins
to the telomere via a distinct linear sequence.
Hyeung Kim et al.
doi:10.1038/nsmb.1575
Abstract: http://links.ealert.nature.com/ctt?kn=43&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Article: http://links.ealert.nature.com/ctt?kn=10&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Polyglutamine disruption of the huntingtin exon 1 N terminus triggers
a complex aggregation mechanism pp380 - 389
The huntingtin protein (HTT) contains a polyQ tract preceded by an
N-terminal flanking sequence (HTTNT) that contributes to HTT
aggregation. Now the role of HTTNT in aggregation is explored
in vitro, revealing a complex, multistep pathway initiated when
polyQ disrupts HTTNT structure, enhancing the latter's assembly
into prefibrillar aggregates. Within these intermediates,
subsequent interactions of the polyQ moieties drive further
assembly into compact amyloid aggregates.
Ashwani K Thakur et al.
doi:10.1038/nsmb.1570
Abstract: http://links.ealert.nature.com/ctt?kn=44&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Article: http://links.ealert.nature.com/ctt?kn=109&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Bacterial frataxin CyaY is the gatekeeper of iron-sulfur cluster
formation catalyzed by IscS pp390 - 396
Frataxin is a conserved protein involved in the cellular assembly
of iron-sulfur clusters, but its exact role is not clear. Now work
on bacterial frataxin CyaY indicates that it acts as an
iron-dependent regulator of iron-sulfur cluster formation by the
desulfurase IscS.
Salvatore Adinolfi et al.
doi:10.1038/nsmb.1579
Abstract: http://links.ealert.nature.com/ctt?kn=61&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Article: http://links.ealert.nature.com/ctt?kn=49&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
The pathway of hepatitis C virus mRNA recruitment to the human ribosome
pp397 - 404
Some viruses, including hepatitis C virus (HCV), bypass cellular
initiation factors and can initiate translation through an internal
ribosomal entry site (IRES). This process is now examined for the
HCV IRES, indicating that conformational changes are necessary but
not sufficient for initiation. Instead, the initiator tRNA, but not
its interaction with the start codon, seems key to stabilizing HCV
mRNA binding to the ribosome, indicating that this IRES bypasses
some, but not all, of the functions of the initiation factors.
Christopher S Fraser, John W B Hershey and Jennifer A Doudna
doi:10.1038/nsmb.1572
Abstract: http://links.ealert.nature.com/ctt?kn=50&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Article: http://links.ealert.nature.com/ctt?kn=95&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Tertiary interactions within the ribosomal exit tunnel pp405 - 411
Although the dimensions of the ribosomal exit tunnel are cramped,
it is known that some structural elements can begin folding there.
The tertiary folding of an alpha-helical hairpin and a beta-hairpin
are now probed within the ribosomal exit tunnel, indicating that
minimal tertiary interactions can be explored close to the exit of
the tunnel.
Andrey Kosolapov and Carol Deutsch
doi:10.1038/nsmb.1571
Abstract: http://links.ealert.nature.com/ctt?kn=65&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Article: http://links.ealert.nature.com/ctt?kn=74&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Acetylation by GCN5 regulates CDC6 phosphorylation in the S phase of
the cell cycle pp412 - 420
CDC6 is involved in the assembly of pre-replicative complexes. CDC6
is now found to be acetylated by GCN5, a modification that leads to
subsequent phosphorylation at sites targeted by by Cyclin A during S
phase, thus regulating stability and subcellular localization.
Roberta Paolinelli, Ramiro Mendoza-Maldonado, Anna Cereseto and
Mauro Giacca
doi:10.1038/nsmb.1583
Abstract: http://links.ealert.nature.com/ctt?kn=23&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Article: http://links.ealert.nature.com/ctt?kn=19&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Regulation of active site coupling in glutamine-dependent NAD+
synthetase pp421 - 429
NAD+ is an essential cofactor in energy metabolism and redox
reactions and is a regulator of different cellular processes.
Kinetic and structural studies of the M. tuberculosis
glutamine-dependent NAD+ synthetase suggests a tight coupling
of the catalytic sites that catalyzes the ATP-dependent formation
of NAD+ at the synthetase domain using the ammonia derived from the
L-glutamine and glutaminase domain.
Nicole LaRonde-LeBlanc, Melissa Resto and Barbara Gerratana
doi:10.1038/nsmb.1567
Abstract: http://links.ealert.nature.com/ctt?kn=96&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Article: http://links.ealert.nature.com/ctt?kn=69&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Precursor-product discrimination by La protein during tRNA metabolism
pp430 - 437
The La protein binds precursor tRNAs at their 3' ends, thus
facilitating maturation. Crystal structures indicate that the most
obvious RNA-recognition motif does not bind this pre-tRNA tail, but
studies now indicate that La has two distinct binding sites for the
pre-mRNA. Recognition through these two sites may help distinguish
precursor from product, an idea supported by biochemical studies here.
Mark A Bayfield and Richard J Maraia
doi:10.1038/nsmb.1573
Abstract: http://links.ealert.nature.com/ctt?kn=11&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Article: http://links.ealert.nature.com/ctt?kn=59&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
S16 throws a conformational switch during assembly of 30S 5'
domain pp438 - 445
Ribosomal proteins are known to play an important role in determining
rRNA structure. The body of the 30S ribosomal subunit is formed by the
16S rRNA 5' domain. New data indicate that the assembly protein S16
discriminates between folding intermediates of the 5' domain,
increasing cooperative 30S assembly and stabilizing interactions at
its decoding site.
Priya Ramaswamy and Sarah A Woodson
doi:10.1038/nsmb.1585
Abstract: http://links.ealert.nature.com/ctt?kn=7&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Article: http://links.ealert.nature.com/ctt?kn=20&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
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BRIEF COMMUNICATIONS
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CK2alpha phosphorylates BMAL1 to regulate the mammalian clock
pp446 - 448
BMAL1 has a central role in the mammalian circadian clock, acting
as a transcriptional activator. The activity of BMAL1 is controlled
by post-translational modifications such as acetylation and
SUMOylation. Now the kinase CK2alpha is shown to phosphorylate BMAL1 at
Ser90, and this is essential for BMAL1's function in the circadian
clock.
Teruya Tamaru et al.
doi:10.1038/nsmb.1578
Abstract: http://links.ealert.nature.com/ctt?kn=86&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Article: http://links.ealert.nature.com/ctt?kn=2&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Distinct transcriptional outputs associated with mono- and
dimethylated histone H3 arginine 2 pp449 - 451
Methylation at particular residues on histone tails has been
associated with various functions and, in the case of dimethylated
histone H3 arginine 2 (H3R2), cross-talk with methylation of a
nearby lysine has been shown to be linked to transcriptional
repression. Budding yeast monomethylated H3R2 is now shown to
be associated with active loci and involved in activation of
meiotic genes upon induction of sporulation.
Antonis Kirmizis et al.
doi:10.1038/nsmb.1569
Abstract: http://links.ealert.nature.com/ctt?kn=36&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
Article: http://links.ealert.nature.com/ctt?kn=38&m=32247654&r=MTc2OTcxOTY5MQS2&b=2&j=NDcxMDI4MTgS1&mt=1&rt=0
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