I have a list of gene expression and i want to separate them based of their quantile in R.
How i can do this?
-quantile (gene_list)
  after that based of quantile the 5 list extracted 
gene_id  read_count
gene1  30
gene2 354
gene3  49
gene4 100
. .
.
 the output i want to be as below
list 1_quantile  0-1
list 2_quantile 1-20
list 3_quantile 20-50
list 4_quantile 50-100
list 5_quantile  >100
```

It appears that you are just asking a question that has nothing to do with Bioconductor tools (just because you are using gene expression data, doesn't mean it's a Bioconductor question). It's also not clear what you want? A list is a specific thing in R, and a gene list might mean a list of genes, or maybe you mean something entirely different. But anyway.

## fake data
> rn <- rnorm(1000)
> quantile(rn, seq(0,1,0.2))
        0%        20%        40%        60%        80%       100% 
-2.6974030 -0.8147699 -0.2391583  0.2748159  0.9112004  3.2960733 
> cuts <- cut(rn, quantile(rn, seq(0,1,0.2)), include.lowest = TRUE)
> levels(cuts)
[1] "[-2.7,-0.815]"   "(-0.815,-0.239]" "(-0.239,0.275]"  "(0.275,0.911]"  
[5] "(0.911,3.3]"  
> lst <- split(rn, cuts)
> sapply(lst, head)
     [-2.7,-0.815] (-0.815,-0.239] (-0.239,0.275] (0.275,0.911] (0.911,3.3]
[1,]    -1.8774472      -0.5442199     0.15592221     0.5735599    1.961777
[2,]    -0.9500052      -0.4153239    -0.23012671     0.5487853    1.838525
[3,]    -1.8244960      -0.5660583     0.09275705     0.8824427    1.557622
[4,]    -1.1705903      -0.6712830     0.21497970     0.5910672    2.210673
[5,]    -1.1879555      -0.4075969    -0.10534529     0.7041176    1.151611
[6,]    -0.9184985      -0.4060458     0.11778675     0.4087296    1.122461

One of those things might be what you are after.