A complex of eukaryotic initiation factors (eIFs) 4A, 4E, and 4G (collectively termed eIF4F) plays a key role in recruiting
mRNAs to ribosomes during translation initiation. The site of ribosomal ...entry onto most mRNAs is determined by interaction
of the 5â²-terminal cap with eIF4E; eIFs 4A and 4G may facilitate ribosomal entry by modifying mRNA structure near the cap
and by interacting with ribosome-associated factors. eIF4G recruits uncapped encephalomyocarditis virus (EMCV) mRNA to ribosomes
without the involvement of eIF4E by binding directly to the â¼450-nucleotide long EMCV internal ribosome entry site (IRES).
We have used chemical and enzymatic probing to map the eIF4G binding site to a structural element within the J-K domain of
the EMCV IRES that consists of an oligo(A) loop at the junction of three helices. The oligo(A) loop itself is not sufficient
to form stable complexes with eIF4G since alteration of its structural context abolished its interaction with eIF4G. Addition
of wild type or trans -dominant mutant forms of eIF4A to binary IRES·eIF4G complexes did not further alter the pattern of chemical/enzymatic modification
of the IRES.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We present a detailed study of the active eclipsing binary V455 Cygni (V455 Cyg), based on spectroscopic and photometric data from the 1.25-m and 0.6-m telescopes at the Crimean SAI Observatory and ...the 0.6-m telescope at the Maidanak Observatory, collected in the period from 2000 to 2010.
Spectroscopic evidence and the shape of the light curves suggest the existence of a geometrically and optically thick accretion disc around the more massive and hotter gainer. We used a model of the binary system based on the Roche geometry and including the accretion disc with active regions to estimate the orbital and physical parameters of the components of V455 Cyg. Our model fits the observations very well for all individual passband light curves.
The evident seasonal changes in the shape of the light curves, including prominent variations in the depth of the eclipses, can be explained by the changes in the parameters of the accretion disc and the active regions of the disc, arising in turn from a variable rate of mass transfer.
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BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
15-lipoxygenase (LOX) expression is translationally silenced in early erythroid precursor cells by a specific mRNA–protein complex formed between the differentiation control element in the 3′ ...untranslated region (UTR) and hnRNPs K and E1. The 3′UTR regulatory complex prevents translation initiation by an unknown mechanism. We demonstrate that the 40S ribosomal subunit can be recruited and scan to the translation initiation codon even when the silencing complex is bound to the 3′UTR. However, the joining of the 60S ribosomal subunit at the AUG codon to form a translation competent 80S ribosome is inhibited, unless initiation is mediated by the IGR-IRES of the cricket paralysis virus. These findings identify the critical step at which LOX mRNA translation is controlled and reveal that 60S subunit joining can be specifically regulated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
According to the generally accepted scanning model proposed by M. Kozak, the secondary structure of the 5'-untranslated region (5'-UTR) of eukaryotic mRNA can only inhibit the translation initiation ...by counteracting migration of the 40S ribosomal subunit along the mRNA polynucleotide chain. The existence of efficiently translatable mRNAs with long and highly structured 5'-UTRs is incompatible with the cap-dependent scanning mechanism. Such mRNAs are expected to use alternative ways of translation initiation to be efficiently translated, primarily the mechanism of internal ribosome entry mediated by internal ribosome entry sites (IRESs), special RNA structures that reside in the 5'-UTR. The paper shows that this viewpoint is incorrect and is probably based on experiments with mRNA translation in rabbit reticulocyte lysate. This cell-free system fails to adequately reflect the relative translation efficiencies observed for different mRNAs in vivo. Five structurally similar mRNAs with either short leaders of the β-globin and β-actin mRNAs or long and highly structured 5'-UTRs of the c-myc, LINE-1, and Apaf-1 mRNAs displayed comparable translation activities in transfected cells and an entire cytoplasmic extract of cultivated cells. Translation activity proved to strongly depend on the presence of a cap at the 5' end.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
36.
Forbidden hugs in pandemic times Cai, Y.-Z.; Pastorello, A.; Fraser, M. ...
Astronomy and astrophysics (Berlin),
11/2022, Volume:
667
Journal Article
Peer reviewed
Open access
We present an observational study of the luminous red nova (LRN) AT 2021biy in the nearby galaxy NGC 4631. The field of the object was routinely imaged during the pre-eruptive stage by synoptic ...surveys, but the transient was detected only at a few epochs from ∼231 days before maximum brightness. The LRN outburst was monitored with unprecedented cadence both photometrically and spectroscopically. AT 2021biy shows a short-duration blue peak, with a bolometric luminosity of ∼1.6 × 10
41
erg s
−1
, followed by the longest plateau among LRNe to date, with a duration of 210 days. A late-time hump in the light curve was also observed, possibly produced by a shell-shell collision. AT 2021biy exhibits the typical spectral evolution of LRNe. Early-time spectra are characterised by a blue continuum and prominent H emission lines. Then, the continuum becomes redder, resembling that of a K-type star with a forest of metal absorption lines during the plateau phase. Finally, late-time spectra show a very red continuum (
T
BB
≈ 2050 K) with molecular features (e.g., TiO) resembling those of M-type stars. Spectropolarimetric analysis indicates that AT 2021biy has local dust properties similar to those of V838 Mon in the Milky Way Galaxy. Inspection of archival
Hubble
Space Telescope data taken on 2003 August 3 reveals a ∼20
M
⊙
progenitor candidate with log (
L
/
L
⊙
) = 5.0 dex and
T
eff
= 5900 K at solar metallicity. The above luminosity and colour match those of a luminous yellow supergiant. Most likely, this source is a close binary, with a 17–24
M
⊙
primary component.
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FMFMET, NUK, UL, UM, UPUK
Forbidden hugs in pandemic times Y.-Z. Cai; Pastorello, A; Fraser, M ...
Astronomy and astrophysics (Berlin),
11/2022, Volume:
667
Journal Article
Peer reviewed
Open access
We present an observational study of the luminous red nova (LRN) AT 2021biy in the nearby galaxy NGC 4631. The field of the object was routinely imaged during the pre-eruptive stage by synoptic ...surveys, but the transient was detected only at a few epochs from ∼231 days before maximum brightness. The LRN outburst was monitored with unprecedented cadence both photometrically and spectroscopically. AT 2021biy shows a short-duration blue peak, with a bolometric luminosity of ∼1.6 × 1041 erg s−1, followed by the longest plateau among LRNe to date, with a duration of 210 days. A late-time hump in the light curve was also observed, possibly produced by a shell-shell collision. AT 2021biy exhibits the typical spectral evolution of LRNe. Early-time spectra are characterised by a blue continuum and prominent H emission lines. Then, the continuum becomes redder, resembling that of a K-type star with a forest of metal absorption lines during the plateau phase. Finally, late-time spectra show a very red continuum (TBB ≈ 2050 K) with molecular features (e.g., TiO) resembling those of M-type stars. Spectropolarimetric analysis indicates that AT 2021biy has local dust properties similar to those of V838 Mon in the Milky Way Galaxy. Inspection of archival Hubble Space Telescope data taken on 2003 August 3 reveals a ∼20 M⊙ progenitor candidate with log (L/L⊙) = 5.0 dex and Teff = 5900 K at solar metallicity. The above luminosity and colour match those of a luminous yellow supergiant. Most likely, this source is a close binary, with a 17–24 M⊙ primary component.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
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