Antisense transcription can regulate sense gene expression. However, previous 
annotations of antisense transcription units have been based on detection of 
mature antisense long noncoding (aslnc)RNAs by RNA-seq and/or microarrays, only 
giving a partial view of the antisense transcription landscape and incomplete 
molecular bases for antisense-mediated regulation. Here, we used native 
elongating transcript sequencing to map genome-wide nascent antisense 
transcription in fission yeast. Strikingly, antisense transcription was detected 
for most protein-coding genes, correlating with low sense transcription, 
especially when overlapping the mRNA start site. RNA profiling revealed that the 
resulting aslncRNAs mainly correspond to cryptic Xrn1/Exo2-sensitive transcripts 
(XUTs). ChIP-seq analyses showed that antisense (as)XUT's expression is 
associated with specific histone modification patterns. Finally, we showed that 
asXUTs are controlled by the histone chaperone Spt6 and respond to meiosis 
induction, in both cases anti-correlating with levels of the paired-sense mRNAs, 
supporting physiological significance to antisense-mediated gene attenuation. 
Our work highlights that antisense transcription is much more extended than 
anticipated and might constitute an additional nonpromoter determinant of gene 
regulation complexity.