Re: Does the gene that codes for the splicing protein contain introns?

   This is an interesting question Sean, and at first blush, it seems like 
a chicken and egg problem, but upon some contemplation we can see that this 
ain't necessarily so.  First let me give a little basic background on RNA 
splicing.  Most genes, both those encoding proteins and those encoding RNA 
molecules (e.g. ribosomal RNA) contain regions of coding sequence (exons) 
separated by regions of non-coding sequence (introns).  When RNA is first 
transcribed from these genes, the RNA contains both the exons and introns 
(this RNA is called heterogeneous nuclear RNA, or hnRNA).  In order for a 
functional end product to result, the intronic sequence must be spliced out 
of the RNA.  The splicing out of introns is achieved through a series of 
steps whereby the intron is cut out of the RNA and the ends of the two 
exons are joined together.  This occurs in the nucleus of the cell and 
involves a complex of small nuclear RNAs and proteins, not just one 
protein.  The small nuclear RNAs (snRNAs) are about 100-300 bases long.  To 
my knowledge, their DNA sequences do not contain introns, however (and here 
is where it gets weird) several of theses snRNAs are encoded by intronic 
sequences from other protein-encoding genes.  The proteins associated with 
splicing belong to a class of proteins which interact with snRNAs to form 
complexes known as ribonucleoproteins (often referred to as snRNPs or 
"snurps").  There are many snRRPs in the nucleus; some function in RNA 
splicing and some function in ribosomal processing and translation.  The 
snRNPs involved in splicing, together with other protein factors, comprise 
a large structure called the spliceosome.  This structure is responsible 
for splicing out most intronic sequences (some RNA sequences can cut out 
their own introns), these introns are recognized because they have GT-AG 
dinucleotides at their 5' and 3' ends as well as a couple of other 
semi-conserved sequences.  The genes encoding the proteins found in the 
spliceosomes do indeed contain introns, which leads directly to your 
question.
   If these proteins involved in RNA splicing are derived from genes which 
need to be spliced, how can this be?  The answer is that the spliceosome 
complex already exists in the nucleus of the cell.  When I say cell, think 
egg.  The egg, or ovum, contains a nucleus, proteins, ribosomes, 
mitochondria, endoplasmic reticulum, i.e., all the structures and building 
materials needed to begin transcription, translation, and cellular division 
once it is fertilized.  The nucleus of the ovum also contains splicesomes 
as well as the individual snRNAs and proteins needed to form additional 
splicesome complexes.  And, when a cell divides it basically splits up its 
furnishings as it were, so that each new daughter cell gets an equal share 
of everything, including the splicesomes.