A first step in understanding the architecture of the spliceosome is elucidating the positions of individual spliceosomal components and functional centers. Catalysis of the first step of pre-mRNA splicing leads to the formation of the spliceosomal C complex, which contains the pre-mRNA intermediates—the cleaved 5' exon and the intron-3' exon lariat. To topographically locate the catalytic center of the human C complex, we first determined, by DNA oligonucleotide-directed RNAse H digestions, accessible pre-mRNA regions closest to nucleotides of the cleaved 5' splice site (i.e., the 3' end of exon 1 and the 5' end of the intron) and the intron lariat branch point, which are expected to be at/near the catalytic center in complex C. For electron microscopy (EM) localization studies, C complexes were allowed to form, and biotinylated 2'-OMe RNA oligonucleotides were annealed to these accessible regions. To allow localization by EM of the bound oligonucleotide, first antibiotin antibodies and then protein A-coated colloidal gold were additionally bound. EM analyses allowed us to map the position of exon and intron nucleotides near the cleaved 5' splice site, as well as close to the anchoring site just upstream of the branch adenosine. The identified positions in the C complex EM map give first hints as to the path of the pre-mRNA splicing intermediates in an active spliceosomal C complex and further define a possible location for its catalytic center.
We investigated the role of cholinergic neurotransmission in olfactory fear learning. Mice receiving pairings of odor and foot shock displayed fear to the trained odor the following day. Pretraining injections of the nicotinic antagonist mecamylamine had no effect on subsequent freezing, w ... more
In Aplysia, repeated trials of aversive stimuli produce long-term sensitization (LTS) of defensive reflexes and suppression of feeding. Whereas the cellular underpinnings of LTS have been characterized, the mechanisms of feeding suppression remained unknown. Here, we report that LTS traini ... more
The anaphase promoting complex/cyclosome (APC/C) is an E3 ligase regulated by Cdh1. Beyond its role in controlling cell cycle progression, APC/C–Cdh1 has been detected in neurons and plays a role in long-lasting synaptic plasticity and long-term memory. Herein, we further examined the role ... more
The human mouth is home to a teeming community of microbes, yet still relatively little is known about what determines the specific types of microorganisms that live there. Is it your genes that decide who lives in the microbial village, or is it your environment? In a study published in ... more
Your genes determine much about you, but environment can have a strong influence on your genes even before birth, with consequences that can last a lifetime. In a study published in Genome Research, researchers have for the first time shown that the environment experienced in the womb defi ... more
The human gut is home to a teeming ecosystem of microbes that is intimately involved in both human health and disease. But while the gut microbiota is interacting with our body, they are also under constant attack from viruses. In a study published in Genome Research, researchers have ana ... more