Members of the HMG-I(Y) family of mammalian nonhistone proteins are of importance because they have been demonstrated to bind specifically to the minor groove of A.T-rich sequences both in vitro and in vivo and to function as gene transcriptional regulatory proteins in vivo. Here we report the cloning, sequencing, characterization and chromosomal localization of the human HMG-I(Y) gene. The gene has several potential promoter/enhancer regions, a number of different transcription start sites and numerous alternatively spliced exons making it one of the most complex nonhistone chromatin protein-encoding genes so far reported. The putative promoter/enhancer regions each contain a number of conserved nucleotide sequences for potential binding of inducible regulatory transcription factors. Consistent with the presence of these conserved sequences, we found that transcription of the HMG-I(Y) gene is inducible in human lymphoid cells by factors such as phorbol esters and calcium ionophores. Detailed sequence analysis confirms our earlier suggestion that alternative splicing of precursor mRNAs gives rise to the major HMG-I and HMG-Y isoform proteins found in human cells. Furthermore, the gene's exon-intron arrangement fully accounts for all of the previously cloned human HMG-I(Y) cDNAs (1,2). Also of considerable interest is the fact that each of the three different DNA-binding domain peptides present in an individual HMG-I(Y) protein is coded for by sequences present on separate exons thus potentially allowing for exon 'shuffling' of these functional domains during evolution. And, finally, we localized the gene to the short arm of chromosome 6 (6p) in a region that is known to be involved in rearrangements, translocations and other abnormalities correlated with a number of human cancers.

Tetra-0-acetyl-pentopyranosen und Penta-0-acetyl-hexopyranosen setzen sich mit Trimethylsilylazid bei Gegenwart von BF3 oder SnC14 leicht zu den entsprechenden Glycosylaziden l a bis 11 um (Tab. I). Es entsteht stets nur das anomere Glycosylazid. in dem die Azidogruppe und 2-OAc ,,trans" zueinander angeordnet sind. In Glycosylaziden sind die Bindungen CI -N, und N,--N, in der Weise polarisiert, daR der Dipol in beiden Flllen zum N, weist. Hieraus wird abgeleitet, daD bei Glycosylaziden wie bei Methylglycosiden ein exo-anomerer Effekt wirksam sein sollte. der die Konformeren 9 und 12 stark bevorzugt. Die Anwendung der Arid-Oktantenregel sagt fur das a-D-Glycosylazid 12 einen negativen, fur das p-D-Glycosylazid 9 einen positiven Cotton-Effekt voraus. Messungen des Circulardichroismus stimmen mit diesen Voraussagen gut uberein, was fur einen exo-anomeren Effekt bei Glycosylaziden spricht. Conformational Analysis, 111 1) em-Anomeric Effect and Circular Didvoism of Glycopyranosyl AzidesTetra-0-acetyl-aldopentopyranoses and penta-0-acetyl-aldohexopyranoses react readily with trimethylsilyl azide in the presence of BF3 or SnC14 to afford the corresponding glycosyl azides l a -11 (table 1). Only the anomeric glycosyl atide having the azido group ,,trans" to the 2-acetoxy group is obtained in each case. The polarization of thc C1 -N, and N, -N, bonds in glycosyl azides is such that in both cases the dipole is directed towards N,. It can be deduced that glycosyl azides, like methyl glycopyranosides, should exhibit an exo-anomeric effect which strongly favors the conformers 9 and 12. The application of the azide-octant rule predicts a negative Cotton effect for the a-D-glycosyl a i d e 12 and a positive effect for the p-o-glycosyl azide 9. Circular dichroism measurements are in good agreement with these predictions, indicating the operation of an exo-anomeric effect in the glycosyl azides.

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Konformationsgleichgewichte von N‐substituierten N‐Pentopyranosiden wurden untersucht. Der anomere Effekt nimmt bei Substitution am C‐1 durch nachstehende Gruppen in folgender Reihe ab: \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ \ominus - \mathop {\rm P}\limits^ \oplus ({\rm C}_6 {\rm H}_5)_3 $\end{document} > OAc > N3 > NHCOCF3 > NHCOC6H4OCH3‐(p) ≃ NHCO‐ C6H4NO2‐(p) > NH2 ≃ NHAc ≃ \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ \oplus {\rm PH} $\end{document}(C6H5)3]Cl⊖ > Imidazoliumsalz ≃ Pyridiniumsalz. Bei der NH2‐Gruppe ist kein anomerer und inverser anomerer Effekt nachweisbar. Die Imidazolium‐ und Pyridinium‐Verbindungen 33 und 31 zeigen inversen anomeren Effekt, wodurch in der α‐D‐xylo‐Reihe Inversion zur triaxialen 1C4(D)‐Konformation eintritt. Dem C1N1‐Dipol wird ein überwiegender Einfluß auf den anomeren Effekt zugemessen. Der Substituent mit negativiertem Stickstoff \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ \ominus - \mathop {\rm P}\limits^ \oplus ({\rm C}_6 {\rm H}_5)_3 $\end{document} weist den größten anomeren Effekt auf, der bei Protonierung des Ylids zur \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ \oplus {\rm PH} $\end{document}(C6H5)3]Cl⊖‐Gruppe vollständig verschwindet.