Similarity between 5'- and 3'-terminal nucleotide sequences and double-stranded RNA-derived sequences of eukaryotic mRNA

It has been reported recently that parts of the nucleotide sequences present in the 5′- and 3′-terminal regions of cytoplasmic mRNA are derived from double-stranded hairpin structures of heterogeneous nuclear RNA—a putative mRNA precursor (Naora, 1979). In order to explore the nature of double-stranded hairpin structures, using the sequencing data of human and rabbit globin mRNA and hen ovalbumin mRNA, we examined the following possibility: that certain regions of both the 5′- and 3′-terminal nucleotide sequences of mature mRNA were present in double-stranded hairpin structures covalently linked to both sides of the message sequence in the precursor mRNA molecule and that these double-stranded hairpin structures are similar to each other. The results support the above possibility by showing substantial similarity of nucleotide sequences between the 5′- and 3′-terminal regions of these mRNAs in terms of the formation of similar double-stranded hairpin structures.     

Human non-lineage antigen,CD46 (HuLy-m5): purification and partial sequencing demonstrates structural homology with complement-regulating glycoproteins

CD46, until recently known as HuLy-m5, is a non-lineage restricted surface antigen ubiquitously expressed by almost all human cells except erythrocytes. The CD46 antigen is identified by the E4.3 monoclonal antibody (mAb) and exists at the surface of human peripheral blood lymphocytes (PBLs) as two acidic, non-disulfide bonded chains, and , ofM _r 66 000 and 56 000. Receptor density analysis showed that CD46 was of moderately low abundance on PBLs with 7.5×10³ molecules present on each cell. The two chains of CD46 were purified (144 000-fold) by immunoaffinity-chromatography with E4.3 mAb from the plasma membranes of a human spleen infiltrated with chronic myelogenous leukemia cells. Amino acid sequence analysis of the NH₂-terminal of both and chains yielded the same sequence; XEEPPQ/TFEAMELIGKPKPYYEIGE. Peptide mapping studies confirmed that both CD46 chains were closely related, except for one peptide fragment. This amino acid sequence is identical to that of the NH₂-terminal of the recently cloned membrane co-factor protein (MCP), a membrane protein that binds the C3b and C4b fragments of complement and acts as a co-factor for I protein-mediated decay of the complement convertases. CD46 shares a cross-reactive epitope with some primate retroviruses, and this may indicate that some retroviruses mimic the mechanisms used by autologous human cells to evade complement-mediated immune clearance. Offprint requests to: I. F. C. McKenzie.     

Problems of ontogeny and phylogeny in brain-size evolution

Fundamental ambiguities in the interpretation of brain/body allometric trends can only be resolved by analyzing relationships between ontogenetic brain/body growth processes in different groups. The ambiguous concept of adult encephalization confuses at least three distinct types of transformation of a common mammalian growth curve: scalar magnification, total curve didplacement, and changes in proportions of the pre- and postnatal phases of the curve. The conservative ratio between pre- and postnatal growth phases determines the apparent linearity of comparative brain/body allometry and can be explained by assuming that embyological neurogenetic processes ultimately determine both target brain and body size—the first directly and the second indirectly via neurohormonal regulation of somatic growth. Uneven taxonomic distribution of different ontogenetic growth patterns may explain many differences in the allometric trends at different taxonomic levels of analysis. The human brain grows exactly as if it was in a giant ape body; however, because of decoupled growth in different brain regions, it regulates body growth as though it were the size of a chimpanzee brain. Human encephalization exhibits an ontogenetic transformation not found in other mammalian groups.     

Movement patterns and herd dynamics among South African giraffes (Giraffa camelopardalis giraffa)

Giraffes reside in a fission–fusion social system, with sex, age proximity, kinship and home range overlap accounting for some of the variance in herd composition, while season, sex, age and time of day influence diet, home range size and distance travelled. To increase our knowledge of habitat use and fission–fusion herd dynamics, we placed GPS devices on eight adult female South African giraffes (Giraffa camelopardalis giraffa) living in the Khamab Kalahari Nature Reserve (South Africa). We tested four predictions about how season, kinship, home range and travel patterns influence habitat use and herd dynamics. Our two key findings were that females with a greater degree of home range overlap were more likely to form herds, but the degree of overlap was independent of the amount of time that they spent together in a herd, and that on the day prior to herd formation, females travelled about twice as far as their daily average and tended to move directly towards their future herd mate. We conclude that habitat use and movement patterns regulating fission–fusion dynamics reflect an interaction of ecological, social and reproductive factors operating in tandem, not independently.     

Observations on the thermoregulatory behaviour of juvenile spotted grunter, Pomadasys commersonnii (Haemulidae: Pisces)

The thermal preference of juvenile spotted grunter, Pomadasys commersonnii (Haemulidae), was determined in a horizontal thermal gradient. Temperature preference was tested over a range of 17–31°C at three salinities. The modal temperature preferenda at 5, 12 and 35 ppt were 25°C, 24.5°C and 25°C, respectively. They were not significantly different. The thermal preferendum of this species was found to be between 24°C and 25°C. Supplementary experiments were conducted to test the stability of the final thermal preferendum. Initial observation of the behaviour of juvenile spotted grunter indicated the presence of a strong circadian rhythm. However, diel variation in activity did not influence temperature preference. These data are important for the development of a culture protocol for this euryhaline species.     

The nfkb1 promoter is controlled by proteins of the Ets family.

The gene encoding NFKB1 is autoregulated, responding to NF-kappa B/Rel activation through NF-kappa B binding sites in its promoter, which also contains putative sites for Ets proteins. One of the Ets sites, which we refer to as EBS4, is located next to an NF-kappa B/Rel binding site, kB3, which is absolutely required for activity of the promoter in Jurkat T cells in response to activation by phorbol 12-myristate 13-acetate (PMA), PMA/ionomycin, or the Tax protein from human T cell leukemia virus type I. We show that EBS4 is, required for the full response of the nfkb1 promoter to PMA or PMA/ionomycin in Jurkat cells. EBS4 is bound by Ets-1, Elf-1, and other species. Overexpression of Ets-1 augments the response to PMA/ionomycin and this is reduced by mutation of EBS4. Elf-1 has less effect in conjunction with PMA/ionomycin, but by itself activates the promoter 12-fold. This activation is only partly affected by mutation of EBS4, and a mutant promoter that binds Ets-1, but not Elf-1, at the EBS4 site responds to PMA/ionomycin as efficiently as the wild-type. Ets proteins may be responsible for fine-tuning the activity of the nfkb1 gene in a cell-type-specific manner.     

DNA-binding properties of antitumor-active cis-bis(pyridine)platinum(II) organoamides

 The interaction of the new antitumor-active platinum organoamide complexes [Pt{N(p–HC₆F₄)CH₂}₂(py)₂] and [Pt{N(C₆F₅)CH₂}₂(py)₂] (py = pyridine) with small G-containing (oligo)nucleotides [GMP, d(GpG)] has been studied to establish whether or not these compounds can bind to DNA in an analogous manner to cisplatin. The reaction products have been analyzed by ¹H, ¹⁹F and ³¹P NMR spectroscopy. From the NMR data it is concluded that the {Pt(py)₂}²⁺ moiety binds to the N7 position of the G base, analogously to cisplatin, with the organoamide ligand acting as the leaving group. For the GG-N7,N7 adduct, structural differences are found for the sugar conformation, compared with cisplatin. These differences may account for the activity of these new compounds in tumor cell lines resistant to cisplatin. Received: 25 September 1995 / Accepted: 7 March 1996