Febs Letters

doi: 10.1016/0014-5793(92)80641-Spmid: N/A

Miyazaki, Yukio; Takamatsu, Tetsurou; Nosaka, Tetsuya; Fujita, Setsuya; Hatanaka, Masakazu

doi: 10.1016/0014-5793(92)80642-Tpmid: 1633853

Subcellular localization of human immunodeficiency virus type 1 (HIV‐1) Tat and Rev was examined using a confocal laser scanning microscope (CLSM). In transfected COS‐7 cells, Tat resided exclusively in the perinocleolar region, while Rev infiltrated fully into the nucleoli. The chimeric Tat in which the nucleolar targeting signal was replaced by that of Rev, which retains trans‐acting activity of Tat, remained still in the perinucleolar region as wild‐type Tat. Perinucleolar distribution of Tat protein suggests the existence of a novel nucleolar architecture that affects transcription.

Ohtani, Hiroyuki; Itoh, Hiroyasu; Shinmura, Toshiki

doi: 10.1016/0014-5793(92)80643-Upmid: 1633860

The photocycle of the light‐adapted purple membrane was studied with a time‐resolved fluorometry apparatus: fluorescence of the sample suspension (>660 nm) was pumped with a 633‐nm cw laser and the temporal change induced by a 532‐nm pulsed laser was measured with a photon‐counting‐type transient recorder. The formation and the decay of the O640 intermediate were clearly observed in the pH region between 4.0 and 11.4. A photochemical cycle of N560 was apparently driven in alkaline suspension (pH > 9.3). An O‐like fluorescent intermediate Q appears and decays with time constants of <0.1 ms and 1.7 ± 0.2 ms, respectively.

Paul, C.P.; Levine, B.J.; Robertson, H.D.; Branch, A.D.

doi: 10.1016/0014-5793(92)80644-Vpmid: 1633862

The viroid central conserved region (CCR) is highly conserved among different viroids and is thought to be involved in viroid replication. A novel tertiary structure occurs in the CCR of native circular potato spindle tuber RNAs. To permit more detailed studies of this structural element, a small RNA oligonucleotide containing the CCR of the viroid genome was synthesized. The tertiary structure of these CCR transcripts was examined by UV‐crosslinking of the RNA, followed by mapping of the crosslink using limited alkaline digestion and classical RNA secondary analysis. The CCR transcript was found to undergo UV‐crosslinking between the same two bases as in full‐length viroid, indicating that the tertiary structure is the same and that the CCR transcript will be useful for the affinity purification of host components.

Brustovetsky, N.N.; Egorova, M.V.; Gnutov, D.Yu.; Gogvadze, V.G.; Mokhova, E.N.; Skulachev, V.P.

doi: 10.1016/0014-5793(92)80645-Wpmid: 1633854

Thermoregulatory uncoupling of oxidative phosphorylation has been studied in heart and skeletal muscle mitochondria of ground squirrels. The respiratory rate of mitochondria in the presence of oligomycin was found to be much higher in winter (in hibernating, arousing, or aroused animals) than in summer. This additional respiration is strongly (arousing animals) or completely (hibernating and aroused animals) inhibited by carboxy‐atractylate (CAtr) and bovine serum albumin (BSA). The CAtr‐ and BSA‐induced decreases in the rate of respiration are accompanied by membrane potential increases. The rate of the CAtr‐ and BSA‐sensitive respiration is proportional to the content of free fatty acids which, in the heart, decreases in the order: arousing > aroused = hibernating > summer animals. Maximal respiratory rates observed in the presence of dinitrophenol (arousing > aroused > summer > hibernating animals) do not parallel the fatty acid level. It is assumed that some heat production in the winter animals is due to fatty acid‐induced, ATPIADP‐antiporter‐mediated uncoupling in heart and skeletal muscle mitochondria. The peak of heat production during arousal after hibernation also includes some other stimulatory effect on mitochondrial respiration.

Green, Beverley R.; Shen, Dingren; Aebersold, Ruedi; Pichersky, Eran

doi: 10.1016/0014-5793(92)80646-Xpmid: 1633855

Using an improved SDS‐PAGE system, the polypeptides of the major chlorophyll a/b light‐harvesting complex of PSII (LHCII) from tomato leaves were resolved into five polypeptide bands. All the polypeptides were matched with the genes encoding them by comparing amino acid sequences of tryptic peptides with gene sequences. The two major LHCII bands (usually comigrating as a ‘27 kDa’ polypeptide) were encoded by cab1 and cab3 (Type I LHCII) genes. A third strong band or about 25 kDa was encoded by cab4 (Type II) genes. Polypeptides from two minor bands of 23–24 kDa were not N‐teminally blocked; their N‐terminal sequences showed they were Type III LHCII proteins. One complete cDNA clone and several incomplete clones for Type III polypeptides were sequenced. Combined with the peptide sequences, the results indicate that there are at least four different Type III genes in tomato, encoding four almost identical polypeptides. Thus, all the LHCII CAB polypeptides have been identified, and each type of LHCII polypeptide is encoded by distinct gene or genes in tomato.

Neville, Craig M.; Schmidt, Jakob

doi: 10.1016/0014-5793(92)80647-Ypmid: 1321728

Fish electric organ is a skeletal muscle homolog in which many muscle‐specific genes are inhibited while acetylcholine receptor is expressed at high levels. The molecular mechanisms underlying this discoordinate regulation have not yet been explored. We have obtained partial sequences for MyoD, myogenin, and myf5 from Torpedo californica and have measured their mRNAs in several organs, using ribonuclease protection. We have found that MyoD and myf5 are expressed at comparable levels in muscle and electric organ, whereas myogenin transcripts could not be detected in either tissue. Acetylcholine receptor α subunit mRNA, on the other hand, is two orders or magnitude more abundant in electric tissue. We conclude that neither the loss of contractile proteins from, nor the enhanced expression of acetylcholine receptor genes in, the differentiating electrocyte is a simple consequence of the abundance of myogenic factor messages.

Anantharam, Vellareddy; Panchal, Rekha G.; Wilson, Andrew; Kolchine, Vladimir V.; Treistman, Steven N.; Bayley, Hagan

doi: 10.1016/0014-5793(92)80648-Zpmid: 1386026

Transcripts encoding four NMDA receptor subunits, generated from the NMDAR1 gene by alternative RNA splicing, have been demonstrated in adult rat brain. RNA transcripts derived from cDNAs encoding each form direct the formation of functional NMDA receptors in Xenopus oocytes. The two amino acid cassettes of 21 and 37 amino acids found in the splice variants increase the positive extracellular surface charge on the subunits and may thereby modulate the functional properties of the receptor.

Mayser, Wolfgang; Schloss, Patrick; Betz, Heinrich

doi: 10.1016/0014-5793(92)80649-2pmid: 1633856

Synthesis of the neurotransmitter acetylcholine in cholinergic nerve terminals is regulated by a sodium‐driven high‐affinity choline uptake system in the plasma membrane. We have isolated cDNAs from rat spinal cord and brainstem which encode a choline transporter (CHOT1). The predicted protein shares considerable amino acid identity and several structural features including twelve putative transmembrane regions with other neurotransmitter transporters. Expression of in vitro transcribed CHOT1 RNA in Xenopus oocytes generated Na+‐dependent choline uptake, which was not seen in control oocytes. Amplification by polymerase chain reaction (PCR) revealed significant amounts of CHOT1 mRNA in brain, cerebellum, spinal cord and, to a lesser extent, heart, but only very low expression in lung, kidney and muscle.

Karlyshev, A.V.; Galyov, E.E.; Abramov, V.M.; Zav'yalov, V.P.

doi: 10.1016/0014-5793(92)80650-6pmid: 1633857

A new transcription unit of the f1 gene cluster was found. The DNA sequencing revealed one long open reading frame. Deletion and frame shift mutation analyses have demonstrated the importance of a corresponding gene product for the F1 antigen biosynthesis. A homology of the deduced amino acid sequence with that of AraC family DNA‐binding regulators was shown. A potential regulatory DNA region is discussed.