Acetylcholinesterase (AChE) plays a key role in terminating neurotransmission at cholinergic synapses. AChE is also found in tissues devoid of cholinergic responses, indicating potential functions beyond neurotransmission. It has been suggested that AChE may participate in development, differentiation, and pathogenic processes such as Alzheimer's disease and tumorigenesis. We examined AChE expression in a number of cell lines upon induction of apoptosis by various stimuli. AChE is induced in all apoptotic cells examined as determined by cytochemical staining, immunological analysis, affinity chromatography purification, and molecular cloning. The AChE protein was found in the cytoplasm at the initiation of apoptosis and then in the nucleus or apoptotic bodies upon commitment to cell death. Sequence analysis revealed that AChE expressed in apoptotic cells is identical to the synapse type AChE. Pharmacological inhibitors of AChE prevented apoptosis. Furthermore, blocking the expression of AChE with antisense inhibited apoptosis. Therefore, our studies demonstrate that AChE is potentially a marker and a regulator of apoptosis.

The genomes of two Sulfolobus islandicus strains obtained from Icelandic solfataras were sequenced and analyzed. Strain REY15A is a host for a versatile genetic toolbox. It exhibits a genome of minimal size, is stable genetically, and is easy to grow and manipulate. Strain HVE10/4 shows a broad host range for exceptional crenarchaeal viruses and conjugative plasmids and was selected for studying their life cycles and host interactions. The genomes of strains REY15A and HVE10/4 are 2.5 and 2.7 Mb, respectively, and each genome carries a variable region of 0.5 to 0.7 Mb where major differences in gene content and gene order occur. These include gene clusters involved in specific metabolic pathways, multiple copies of VapBC antitoxin-toxin gene pairs, and in strain HVE10/4, a 50-kb region rich in glycosyl transferase genes. The variable region also contains most of the insertion sequence (IS) elements and high proportions of the orphan orfB elements and SMN1 miniature inverted-repeat transposable elements (MITEs), as well as the clustered regular interspaced short palindromic repeat (CRISPR)-based immune systems, which are complex and diverse in both strains, consistent with them having been mobilized both intra-and intercellularly. In contrast, the remainder of the genomes are highly conserved in their protein and RNA gene syntenies, closely resembling those of other S. islandicus and Sulfolobus solfataricus strains, and they exhibit only minor remnants of a few genetic elements, mainly conjugative plasmids, which have integrated at a few tRNA genes lacking introns. This provides a possible rationale for the presence of the introns.Iceland has been a rich source of hyperthermophilic crenarchaea over the past 3 decades and especially of acidothermophilic members of the order Sulfolobales. Many Sulfolobus islandicus strains ("Island" is German for "Iceland") have also yielded many novel viruses showing varied and sometimes unique morphologies and exceptional genome contents. These properties are consistent with these viruses constituting an archaeal lineage distinct from those of bacteria and eukarya, and they have now been classified into several new viral families (38, 63). In addition, a family of conjugative plasmids has been characterized, with most members deriving from Iceland, which appear to conjugate by a mechanism unique to the archaeal domain (18,37).Although the availability of genome sequences of Sulfolobus strains and their genetic elements has yielded important insights into the biology of these model crenarchaea, a major impediment to more detailed insights has been the paucity of robust and versatile vector-host systems for genetic studies. A few Sulfolobus species have been successfully employed as hosts for such systems, including Sulfolobus solfataricus strains P1 and 98/2 (22, 58), Sulfolobus acidocaldarius (57), and S. islandicus strain REY15A (54). To date, the genetic tools developed for the latter host are the most versatile and include the following: (i) Sulfolobus-Escherichia coli shuttle...