Worm Breeder's Gazette 10(1): 57

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Studies on the C. elegans H1 Histone Family: A Polyadenylated H1 Gene with an Intron, and Evidence for a Sperm-specific H1 Transcript

M. Sanicola, G. Childs and S. Emmons

We have cloned and characterized one member of the C.  elegans H1 
gene family, hhl-1, and our studies have shown it has several features 
atypical of a histone gene.
hhl-1 was isolated from a Bristol clone bank by cross-hybridization 
to a sea urchin H1 gene (L.  pictus).  hhl-1 hybridized to four 
genomic fragments in a Southern blot of genomic DNA digested with 
various enzymes.  We therefore estimate the H1 gene family contains 
four members.  None of these genomic fragments hybridized to a clone 
containing core (H2A, H2B, H3, H4) histone genes, and an analysis of 
cosmids which overlap hhl-1 indicate there are no other histone genes 
nearby in the DNA surrounding hhl-1.  These results support our 
original studies which indicated the core genes are clustered together,
whereas the genes for H1 reside elsewhere in the genome.
The nucleotide sequence of hhl-1 has also revealed properties which 
are unusual for a histone gene.  hhl-1 has a poly(A) addition signal 
and Northern blots have confirmed the hhl-1 transcript fractionates 
with poly (A)+ RNA.  The core histone transcripts of C.  elegans (like 
most histone transcripts from other organisms) are not polyadenylated. 
The hhl-1 sequence is interrupted by a 100 bp segment bounded by C.  
elegans splice donor and acceptor sequences.  The presence of an 
intron has been confirmed by S1 nuclease analysis of transcripts.  
Only the Tetrahymena H1 gene has previously been shown to have an 
We have shown that C.  elegans core genes share unique 5' and 3' 
consensus sequences that are putative sites of action of regulatory 
proteins.  hhl-1 does not have these sequences.  In addition to a 3' 
poly (A) addition signal, analysis of the upstream region of hhl-1 
revealed a consensus sequence for the general transcription factor SP1.
These observations suggest C.  elegans H1 genes are regulated 
independently of the core genes.  We plan to pursue the problem of 
histone gene regulation by studying DNA binding proteins and 
expression of transgenes.
Recently, we have identified a possible tissue-specific histone 
transcript.  In collaboration with Dr.  Sam Ward (Carnegie Institution)
, we have determined there is an H1 transcript which can only be 
detected in poly (A)+ RNA fractions from worms producing sperm (i.e., 
males and fem-3 homozygotes).  It is absent from RNA from worms which 
do not produce sperm (i.e., old adult worms or fem-1 homozygotes).  
This sperm-specific transcript has a larger molecular weight than the 
hhl-1 mRNA found in all worms, and we are currently trying to clone 
the cDNA for this transcript.